There is no simple answer to this, though if you ask around I bet a lot of people would answer: just be yourself. This is probably correct advice, but what does it really mean? It probably means: don't be tempted to tell lies or pretend to have tastes, opinions etc that are not yours.

At the same time, why not be nice? Too many people go on a first date and are actually rude, which may be honest but isn't very helpful. If you are friendly, interested in the other person and not too stubborn (for example, if they want to eat somewhere that wouldn't be your choice, you can give it a try) there is no reason why they shouldn't find you likeable.

Another tip is: don't keep talking about yourself and, especially, don't sit moaning about all the past partners who have treated you badly! (Sorry if you wouldn't do this, but it's a top complaint from people who have had unsuccessful dates).