Of course, one has to consider whether it's a formal, semi formal or casual affair. Whichever it is, there are three rules I abide by; make sure the garment/s chosen are understated and always elegant; choose accessories carefully; and have a bloody good time enjoying the anticipation of the evening to come!
So, which garment to wear?
Formal. That can mean black tie or it can mean simply formal. My favourite style of evening dress hands down features an empire waist.