Buy low, sell high.
I got plenty of other worthless platitudes to go with that one, should you be interested.
Seriously though are you completely inexperienced sailing and wanting to know how to get started or do you have some experience and want advice on how to proceed?
If the later then consider these questions:
-How much sailing experience?
-Are you looking to cruise
extensively or liveaboard
and occasionally take several weeks or months off to nip around the Caribbean
or do you just want to go out for a bit every once in a while?
-How many people as regular crew? Any kids
-What's your budget
to buy and outfit the boat? (living and cruising costs extra.)
-Where are you? Where do you want to sail out of? Which coast do you want to set off from and more specifically where on that coast?
-Where to you want to go?
-Any really strong preferences to start with? (full/fin keel
, mono/multi, spade/skeg/attached rudder
, sloop/cutter/mizzen rigged)