Your job is to drop big enemies before they get close. Don't miss your weakspot shots.
Get a Barrett, stack damage and bullet stumble as much as you can, reload speed to work the action quicker. Get a good non-deagle side-arm to help with hordes when there isn't a special. Keep your head on a swivel and be the first to see the bad guys. Turn on subtitles to be sure you don't miss a spawn.