As stated, it is really pretty simple.
1. Check Sponsors on this forum.
2. Get TOTAL cost quote to avoid surprises.
3. Periodically check to see if a better offer appears and change if appropriate.
Since you are a first timer, a couple notes: Don't get upset when you are asked to sign credit card bill up front. It is a good idea to snap a couple photos of car before you leave rental lot when picking up the car. Check to make sure your cc covers Collision to enable you to decline Collision coverage. You will quickly learn that driving in SXM is an adventure.