As much as i hate spam, i find it to be a good idea to grenade spam a small room with a pesky alien in it, hopefully provoking it out so more effective weapons can be used.
Turret spamming involves bilding piles of turrets in one place, effectively turning whatever comes into their sensor range into swiss cheese.
Of course, the aliens have etremely good spamming stuff, like the acid tube, which, when used in tandem with the trapper, is an extremely effective,(and annoying)way of blocing off a small passage way.
Learn the tricks of spamming, even if you dont use it yourself, the knowlege may come in handy when facing a pesky spam-zone.
Good luck
