Instructions
Run out to the outlying areas of the map in the early levels. This is where the enemies first appear. The foes are easy to kill in the first few waves, so advancing away from the center of the map gives you the first chance to kill them. After the first few waves, stay near the center and play safe because you die easily if you start shooting alone.
Grab the sniper rifle when it appears on the map. The location varies by map. Use this weapon to take out enemies at long range before your teammates shoot with short range weapons.
Place your frag grenades on walls in narrow corridors. That way when an enemy passes by, the grenade blows them up to give you more points.
Help your fallen teammates. Most of the time when enemies weaken your fellow players, they fall but do not die immediately. If you run over to a fallen and help revive before they die, you earn big bonus points.
Place shields to create a base to keep the enemies out, protecting you from harm as you mow down enemies with your weapons.
Survive as long as you can. If you die during a wave, your teammates rack up points while you sit out until the next wave.