DON'T let your outfit speak too loudly. You want it to be loud but not obnoxious. Avoid wearing too much jewellery but don't make it hard to concentrate on how nice your outfit looks. Focus on one piece to be the centrepiece and compliment it with jewellery that matches.
DO experiment with colours. Black and white seem to be everyone's fallback colours (I know I'm guilty of that) but at the same time, if you truly want to stand out, nothing catches peoples eyes more than colour. Try to really make yourself "pop". Not saying that all black everything isn't okay sometimes.
DON'T pick two overly obnoxious colours to go together. You want one main colour to focus on, make sure your colour patterns don't clash with each other or you could end up looking like a hot mess.