You need to know the person's movement and rotation speed depending on the current weapon.

with knife you run faster
with flamethrower and rocket launcher you run slower
with machine gun you run and turn significantly slower

It means, if you are planning a long sprint, select a knife, but be ready to switch to something more robust. Also, it means if somebody is chasing you with a machine gun, you may run faster with a knife.

Weapon switching takes no time, so, if you start to shoot from an assault rifle or minigun, you may suddenly switch to sniper rifle or rocket launcher to deal strong damage and the end of your attack.

Reloading ammo takes a couple seconds, but they are extremely long if you are in combat. So, if you are running out of ammo, better switch to another weapon, instead of waiting for reload.

Map control is very important for victory - items appear on map each 30 seconds. Most important is armor, if you are taking armor each time it spawns on the map, you will be able to survive longer.

Armor protects you by formula - 2 points of armor to 1 point of health. It means, if you have 55 armor and 26 health, and something strike you for 75 damage, you will survive with 1 health and 5 armor, because armor consume 2/3 of damage (75 * 2 / 3 = 50) and the rest will be applied to your character.

If you are playing from a personal computer, do not forget to redefine keys. We are suggesting to make

knife - 1
pistol - 3
shotgun - 2
assault rifle - Q
sniper rifle - E
flamethrower - F
machinegun - SHIFT
rocketlauncher - C

Shotguns have the shortest range. Pistol, assault rifle and machine gun are average ranged weapons. Sniper rifle and rocket launcher outrange them all. Flamethrower designed and "defensive" weapon, which may be used to stop or slow enemy advance.