Symmetrical, smooth, two base with plentiful amounts of Carbines and Battle Rifles. MLG maps also usually lack main power weapons.
if u want a very good tutorial guide thingymobober, heres a really good one: http://www.forgehub.com/forum/halo-forge-discussion/28479-jays-guide-mlg-layouts-scenery.html
how bout here?: http://www.forgehub.com/forum/halo-forge-discussion/28479-jays-guide-mlg-layouts-scenery.html