I reckon budget and mooring sizes would be the main initial considerations, then just get yaself round the brokerages to poke, prod n feel a few to see what you fancy, theres no substitute for actually being on board to get a proper sense of what they are like. NYA, NBS, and Waterside to name but three, all good places to nose around.
Of course once you get a few in mind post on here for opinions and views etc