Find somewhere out of the way and, like the stealthy strategy above, let everyone else soak up the damage and thin themselves out before you walk in fresh and with plenty of health and ammo.
Of course, you can always switch to being more aggressive and combat-focused at any time, but waiting until you are sure to win a fight or until you are attacked can save you a lot of stress and health. Find somewhere out of the way and, like the stealthy strategy above, let everyone else soak up the damage and thin themselves out before you walk in fresh and with plenty of health and ammo.