Well, first of all, I would suggest that you rent to start out, and make sure that the bike fits you. Keep in mind your height and weight. Long legs, short legs...long arms? Short? etc. A reputable and responsible bike renter or dealer would know how to fit you to the correct size bike. You will want a bike that feels comfortable, and I don't mean just the seat either. The whole thing needs to feel right so that you have the confidence to try it out. Secondly, as someone else mentioned above, I would have a friend help you learn to ride. This is the same concept as when a small child learns... someone hangs on to the seat and helps balance the bike for a few paces until you find your own balance. The best advice of all, I think, is to just do it. Get it into your head that you can ride and then you will.