Yes i crossdress and i need some tips?

this guy asked me to be his date at this wedding, and i want to look good (but of course not out do the bride) anyways i have a long black halter dress, and i need to bring my waist in, what should i do to accomplish that and should i wear stockings and a garter belt or pantyhose. what kind of bra should i wear, and should i wear a slip. Oh andi need a pair of panties that are comfortable and can hold me in down there, a pair that will be good for a long day. Please help me look beutiful