For first timer's I usually suggest two ways - if you want to motor-sail across from Miami/Biscayne Bay to Gun Cay and/or
Bimini, then look for winds and seas that are at their minimal (i.e., less than 15kts and less than 3 feet). Usually this occurs when the winds are southeast to south.
Secondly, to sail across without an
engine operating, then you need winds from the South to West. This is because you will be pointing the
boat southeast to try to compensate for the northward
current of the Gulf Stream.
There is a technique called "minimum time crossing" which involves taking a heading of not further southward than 105° magnetic. This keeps the boat moving eastward at your best sailing speed and you accept any northward offset caused by the Gulf Stream. Once you get close to the other side you can sail north or south to find your chosen entry point onto the
Bahamas Banks.
Assuming a desired entry onto the Bahamas Banks near Gun Cay to
Bimini, you need to compensate for about 25nm of northward movement caused by the Gulf Stream. If you started your crossing 25nm south of Gun Cay and Bimini on the
Florida side (down around Key Largo) and sail eastward you would end up on the other side by Gun Cay and/or Bimini. Check a map to measure the offset you would need.
What you do not want to do is end up pointing the boat south-southeast trying to hold a course line and make zero or minimal (1 or 2 kts) speed over the ground towards the Bahamas. I also recommend a day crossing or a departure at or before sunrise to avoid being out in the Gulf Stream after dark when all the
Cruise Ships are trucking south like big rigs on I-95.
Be sure to have the Explorer
Charts before you leave Miami, etc., they are available in West
Marine and other boating/chart stores. My favorite entry point onto the Bahamas Banks is an Explorer Chart waypoint named "Triangle Rocks" which is about half way between Bimini and Gun Cay. It has a very wide open and deep, safe entry onto the Banks. Once on the Banks you can proceed, or
anchor behind Gun Cay or over by the "sunken ship" for some snorkeling, etc.