Here's some instant experience for you all, just add water:
THE MELEE SYSTEMhttp://www.youtube.com/watch?v=rL7VrU6upCA&feature=player_embedded
The general system is: Light attack > Heavy attack > Block > Light attack. If you block a light attack follow quickly with a Light Attack of your own to do a Counter Move that stuns the opponent. Heavy attacks also stun in certain situations. Experiment with it because there are a lot of ways to do the wrong thing and die, and there are many combos that work against different match-ups. I've listed a few below, but far from all.
How to kill a Marine as an Alien:
Hold shift and press Mouse one to pounce, then do a heavy attack (mouse 2).
Sit on a wall / Hang from a roof and headstab them with your tail, kills instantly.
How to kill a Predator as an Alien:
Sneak up on them, predators are very strong head to head against aliens. Try and stun them with your tail and finish with a grab or more tail, light attacks are not very good against Predators. Use your mobility and circle around them but watch out for their tracking heavy attack.
How to kill a Marine as a Predator:
Hold shift and press mouse 1 to pounce, finish with anything.
If a Marine surprises you flat footed get a sprinting start and do a focus pounce. The Marine will be knocked on his back and completely hosed (or you'll eat shotgun in the face, one of the two).
How to kill an Alien as a Predator:
Block the first blow and do a light attack, follow with a heavy and finish with a light or grab. If the aliens first blow is a heavy (tail) break with a light attack and follow with a heavy, finish with light or grab.
If you get the drop on an alien the best opener is the pounce from range or a light attack from behind. After your first move the alien will be stunned for a split second, follow instantly with a heavy attack and finish with a light attack.
How to kill an Alien as a Marine:
SHOOT IT, if it gets too close, block the first blow and do a quick rifle-butt and the alien will be knocked onto the floor and your weapon will automatically track the alien. If the alien starts with a tailwhip try to break it with a quick riflebutt and die.
How to kill a Predator as a Marine:
SHOOT IT, if it gets too close SHOOT IT MORE. If you manage to block a light attack do a rifle-butt and the predator will become stunned for half a split second. Your rifle will gravitate towards a head shot. You have a moments chance to take that head shot before the Predator exits stun and kills you.
Or if you don't like complexity SPAM E TO WIN. When you SPAM E TO WIN you always win, but you also often die. How is this possible? When you SPAM E TO WIN you are locked in a kill animation for up to 7 seconds, so anyone that happens to run past can give you a friendly Tail/Bullet/Combistick in the back of the head free of charge.
Marine is the class you play when you want to poo poo your pants. The game appears darker, you have a smaller FOV, and you're armed with mediocre guns and the worst flashlight ever created. Appearently, in Aliens canon, flashlights are powered by the same batteries found in calculator watches.
Mouse2: Alt Fire (usually owns)
Mouse3: Melee (tap)/Block (hold) (you should probably rebind this to Q)
Q: Sprint (you should probably rebind this to shift)
H: Health Syringe
Number Keys: Weapons change
Health: the Marines' health system is reminiscent of Far Cry 2. You have 3 segments to your health, and each one recharges individually - if you lose one and a half segments, only the 2nd one will recharge. When you use a syringe (green pickups - you spawn with 2 and can hold 3) it takes you back to full health.
Motion Tracker: It tracks motion! This thing is way useful and you should be looking at it. It will even detect motion behind you, however it won't show range for that unless you turn around. And remember, just because the room ahead looks clear doesn't mean it is. If there's movement but you don't see anything, look up!
Watch out for alien blood! It's toxic. Doesn't do a lot of damage, but if you're way low on health it can gently caress you over.
• Pulse Rifle
Fire - Automatic fast firing.
Alt Fire - Grenades (yellow pickups on map)
The pulse rifle is your starting weapon, and it kind of owns. It has a massive loving clip, and you can pick up grenades that do a decent amount of damage. The downside is that it doesn't do a lot of damage and it has a huge muzzle flash that can make it impossible to see what you're firing in dark areas. A direct hit from the alt fire grenade kills anything. The grenade is affected by gravity so the further you want it to go, the higher you have to aim. Don't be afraid to shoot the grenade launcher at close range, you have to be litteraly point blank to die from the splash damage.
Pickup locations: Default weapon, ammo is common around the map.
Grenade pickup locations: All over the map.
Fire: Semiautomatic shootin' a dude
Alt Fire: 3 shot burst
Pistol has infinite ammo, but don't use it. Thing blows.
• Shotgun [heeeelll yeah]
Fire: Shoot a dude with one barrel
Alt Fire: Shoot a dude with two barrels (this is the correct way to shoot a dude)
Alt fire can take down an alien in one hit if you're lucky, but you'll probably want to press that button a few times just in case. The range is really drat short though, so just let the melee classes come to you.
Pickup locations: Symmetrical room with side ramps, storage room, elsewhere(?)
• Sniper Rifle
Fire: Shoot a dude
Alt Fire: Zoom
The sniper rifle is pretty lame, at least on the map in the demo. It's really only useful in the hangar, which is also the only place it can be found AFAIK. It can kill a Predator in two shots, and a headshot is a one-hit kill, and it can see through cloaked Predators with it's night-vision scope. However, it's really not worth it since you'll rarely be doing long-range combat. This will shine more on outdoors maps.
Pickup locations: Hangar raised platform
Fire: Shoot a dude... with fire!
Alt Fire: Napalms the floor in front of it.
Does a lot of damage, but has hilariously short range, and you can't see poo poo for all the fire in your face. Avoid it.
Pickup locations: Connects the hangar and ramp rooms (middle of second floor)
• Smart Gun
Fire: Shoot a dude, but with autotargeting!
Alt Fire: Toggle auto-seeking
This gun is really cool. It automatically targets your enemies (including your species in standard DM, so watch out if you're playing species DM), and does quite a bit of damage. While firing, you can't move very quickly, and you can't sprint while holding it. It also takes up both of your weapon slots. Use this to show your fellow marines where to shoot.
Pickup locations: Hangar raised platform
As an Alien, you are the best dick ever. You can sprint like a motherfucker away from or towards anything, you can run circles on the ceiling confusing your enemy (and yourself), and you can do all sorts of crazy poo poo that can destroy marines.
Mouse1: Claw (Light Attack)/Pounce (in Focus)
Mouse2: Whip Tail (Heavy Attack)
Mouse3: Transition (see below)
Space: Jump/Jump to Surface (see below)
R: Hiss (be a dick to marines who are making GBS threads they drawers)
Surface transition - Basically, this means running on walls and poo poo. By default, you have to use Mouse3 to do this, however, this can be turned off in options so you can own like a motherfucker and not spend half a second waiting to get on a wall. It is still used to quickly go from ceiling or wall to floor with that option off, however.
Jump to surface - This is a really obscure one. Basically, your crosshair will turn from having one vertical line to having three when you aim at a surface you can jump to (any surface within a certain range). Hitting space will jump to that surface and rotate you in air.
Sprint - Use this all the time. Aliens are so fast that they can run any time they're getting shot.
Stealth: Your cross-hairs will fill with black when the game thinks you're hidden in shadows, the game is actually pretty good at judging this.
• Claw: Wave at people to turn them into mush, does not use an aiming laser and has unlimited ammo. Comes with 5 fingers.
• Tail: The aliens heavy attack. Hang from the roof and poke marines in the head with this for instant kills. When using "E" to sneak kill. remember to wash your tail afterwards. Hygiene is important.
Mouse1: Left Stab (Light Attack)/Pounce (in Focus)
Mouse2: Right Stab (Heavy Attack)
Mouse3: Fire Secondary Weapon (See below)
Space: Jump/Jump to Ledge (see below)
F: Switch Vision Mode
1: Select Plasma Caster
2: Select Disc
3: Select Mines
4: Select Combistick
Cloak: Stand still and you're undetectable by humans unless they have a Smartgun with auto-tracking enabled. Aliens couldn't care less about your cloak. All weapons break stealth when used. The faster you move the less you'll look like a cloaked Predator and more like a vampire from twilight. When moving in a dark area (such as the beams in the hangar) turning off your cloak to minimize shimmer is advised against marines.
Jump to ledge: While in Focus you can target any ledge and jump to it, this is very useful to get to places and to escape dire situations. The predators focus jump has varying windup depending on the angle and distance of the jump. Take this into consideration when moving during combat. A short jump might be better to get away from an alien then a long jump.
Secondary Weapon: The predator weapon system works like this. You have your claws out, this is your primary weapon. You can pick up up to 4 additional weapons and select them using your number keys 1 - 4:
• Claws: This is your Primary weapon. Do not underestimate these, they tear aliens apart and completely ruin the day of any Marine that steps within 20 yards of you. The claws combo greatly with the Plasma Caster: Caught off guard? Tap a quick plasma on the target and follow up with a Pounce and rip into it with your claws!
• Combistick: Throw it at people to one-hit-kill them. It has no targeting laser, has a short 2 second cool-down but unlimited ammo. It's a sneaky sniper but hitting a moving target is hard as hell. Experiment with using this in combination with the Visor zoom function. Be careful to not tunnel-vision too much though, or you'll end up Alien snack.
Pickup location: Top of a crate in the corner of the hangar (And more?)
• Plasma Caster: Short tap to fire small stunning bolt, hold to charge and blow poo poo up. When charging a targeting laser appears and locks on your target for tracking. This laser is visible to everyone and expect to get noticed instantly when aiming this thing.
Pickup locations: Vent in the hangar and middle of corridor on the bottom floor below the big room.
• Disc: Throws a Frisbee of Death at your aiming laser, it bounces around and follows your lead to an extent. The laser is active for the entire duration and will draw attention to you. Kills instantly when it hits.
Pickup location: Top of the ledge in the middle of the alien infested area (And more?).
• Mines: They're proximity mines. Throw them behind you in one direction and aim in the other to fool aliens into a reverse ambush.
Pickup location: Top of the beams in the hangar (And more?).
The Mines and the Plasma Caster use Energy. Energy can be recharged at glowing energy boxes found throughout the map. This takes a few seconds and is very likely to get you killed if you're not cautious.
http://steamcommunity.com/id/wolfpackclan - My Steam Profile