airport extreme set up

hi, right, joiner asking from the uk, so be gentle,!!!!!just bought a 5th gen. airport extreme, apple set it up with me . i have a dsl phone line that goes into a belkin g router/modem, then an ethernet cable joins to my extreme. what are the best settings? , tweaks i can make, for xbox, signal , dchp or pppoe , listen to me!!!sounds like i know what im on about, but you guys do , regards, tim