1) Dual weilding is your friend:
Barrettas, Lever Shotguns, and Clock 18c's can all be dual weilded. They let you put out a stream of fire and kill easily. Glocks eat ammo for breakfast so watch it. Lever Shotguns have long reloads but two shots normally can kill a person from a distance but up close only one should be required. Barrettas are the weapon of choice due to fast reload, quick shooting (based on how fast you can click), and good accuracy (allowing for a continuous chain of head shots).

====Tip for dual weilding====
Watch your ammo

~Zockman

2) Quality lowers quantity:
Even on fast computers, like mine, if you lower the quality you can move, shoot, and kill faster. That makes the difference in 100 kills of 300 kills. Hey, I admit it. It looks cooler, but if you are going for badges I suggest lowering the quality and turning off the effects.

====Tip for speed====
Quality is the inverse of quantity (of kills)

~Zockman

3) Ammo is everything
You can't shoot if you don't have ammo! Guns vary in how fast they need more ammo, but they all do. Don't move around just to move, know where the ammo drops are and make a path between each one.

====Tip for ammo====
Know fast how your guns use ammo

~Zockman

4) Know your weapons:

Barretta 92fs:
Reload: fast
Accuracy: good
Rate of fire: Basically, as fast as you can comfortably click.
Damage: low-medium
Clip size: 15,30
Semi-Automatic
Notes: Pistol, dual-weildable, good choice

Rebound Gun:
Reload:
Accuracy: medium
Rate of fire: slow (will not shoot until other bullets are gone from last shot)
Damage: low-medium
Clip size: 10
Semi-Automatic
Notes: Shotgun, bounces off walls, hard to use if you are to close to target, as it will go through the enemy without damage (as far as I can tell)

Tavor:
Reload: Medium
Accuracy: good
Rate of fire: fast
Damage: medium
Clip size: 30
Automatic
Notes: Machine gun, good gun, good backup

Pancore JACKHAMMER:
Reload: SLOW
Accuracy: low
Rate of fire: fast
Damage: medium-high
Clip size: 20
Automatic
Notes: Shotgun, though the Pancore looks like a shot gun it does not give one shot kills like other shot guns, fast rate of fire, small clip size, and slow reload time make this shot-gun appealing, however, it is a pain to keep reloaded.

Glock 18c:
Reload: medium-fast
Accuracy: LOW
Rate of fire: Insane
Damage: medium
Clip size: 30,60
Automatic
Notes: Automatic pistol, can spray bullets everywhere, dual-weildable, EATS AMMO

Lever-Shotgun:
Reload: medium to slow (dual weilding makes reload, at least seem, more the double as long)
Accuracy: low-medium
Rate of fire: slow
Damage: high
Clip size: 7,40
Semi-Automatic
Notes: Shotgun, dual weildable, 2 shots at long range should kill (good with dualweilding), watch your ammo

Lead Pipe:
Reload: N/A
Accuracy: N/A
Rate of fire: medium
Damage: medium
Clip size: N/A
N/A
Notes: Melee, three "head shots" equals one kill, press "Q" to equip, good old stand-by

Tompson SMG:
Reload: medium-fast
Accuracy: low
Rate of Fire: fast
Damage: medium
Clip Size: 35
Automatic
Notes: SMG, starting gun, it's an ok gun, but I'd get a different one

Proxy Mine Launcher:
Reload: slow-medium
Accuracy: medium (explosive, arcs)
Rate of Fire: slow
Damage: high
Clip Size: 1
Manual
Notes: Explosive launcher, good damage, but gets ineffective when you are facing more then one enemy, slow rate of fire due to 1 shot clip size is the main problem, sticks to surfaces and explodes on contact

Acid Bomb Launcher:
Reload: fast
Accuracy: medium (acid cloud, arcs)
Rate of Fire: slow
Damage: medium-high (steadily damages anything in the acid cloud)
Clip Size: 5
Semi-Automatic
Notes: Specialty gun, good for the enemy to clear you out from camping spots, can be useful but pick a different gun if you want to actually kill a lot of enemies fast...er

Lazer Rifle:
Reload: medium
Accuracy: medium-good
Rate of Fire: Basically, as fast as you can comfortably click.
Damage: high
Clip Size: 7
Semi-Automatic
Notes: Special gun, high damage, gibbing abilities, gun good, but small clip size severely limits its viability

Grenade Dart Launcher:
Reload: medium-fast
Accuracy: medium (arcs, explosive)
Rate of Fire: slow-medium
Damage: high (explosive)
Clip Size: 6
Semi-Automatic
Notes: Explosive launcher, will stick to surfaces or enemies and after about 1 second (on walls, floors, etc.) to 3 (on enemies) will detonate

M1187:
Reload: slow
Accuracy: medium
Rate of Fire: medium-fast
Damage: high
Clip Size: 7
Semi-Automatic
Notes: Shotgun, a nice gun this is the next best thing behind Lever-Shotguns

Magnum:
Reload: slow
Accuracy: good
Rate of Fire: slow-medium
Damage: medium-high
Clip Size: 6
Semi-Automatic
Notes: Glorified pistol, overrated (in this game) to slow to reload and fire combined with small cip size makes this a bad choice

====Tip for kicking butt===
Use the guns you're comfortable with

~Zockman

5) Know your map:
Know these things in oder to win:
1. Enemy spawn points (no one can complain if you spawn kill)
2. Ammo drops (you have to have ammo. See #3)
3. Map layout (don't waste time exploring. Know the layout before hand)
4. Choke points (like the door in the medium house map, small opening and only one way in and out)
5. Camping spots (camping is cheap, so are winners)
6. Ammo paths (see #3)

====Tip for saving time====
Explore on easy then go for it on hard

~Zockman

6) Difficulties are different
Simply put, the difficulty changes how easy it to kill an enemy. My guide is based on casual mode

====Tip for using this guide====
My guide is for casual mode. Application to hard mode will change some things.

~Zockman