Presuming you have done the initial legwork in terms of research into suitable vessels as well as financing options and come to the decision that you can afford the purchase, the first thing you will need to do is locate a seller. There are a number of very useful and professionally run boat brokers that can be found online that include listing of the new and second hand boats that they currently have for sale.
These sites typically offer the fairest prices as unlike private sellers they have a good understanding of the market and industry in general. Auctions are another option but prices can be unpredictable. Whichever method you opt for its highly recommended that a reputable surveyor checks the condition of the vessel before any money is exchanged.
Before heading out on your new boat you need to do a comprehensive check of all safety equipment on board. You should also take on the sufficient insurance coverage in case your boat or another one suffers damage. Finding the best insurance deals will again require some research but never the less its better to be safe than sorry so insurance should be purchased before heading out.