Rigging Your Fins
Fins are simple devices. For cave and technical diving, short, stiff fins like the ScubaPro Jet Fins work best. They're heavy and negatively buoyant in the water; this improves your trim. They're stiff which helps with the short, stilted fining cave and wreck divers use to avoid stirring up silt, yet they provide a lot of thrust when needed. The fins also hold about two cups of water each which, when cave diving, comes in handy to wash dirt off your feet when you get back to your car. Avoid the fancy new "Split Fin" design. While I haven't conducted objective, controlled tests to see if this design works, intuition and the consensus of most other experienced divers tells me it doesn't.
Jet Fins come standard with rubber straps which you should immediately replace with spring-straps. These allow you to don/doff the fins very quickly, yet they are very rugged and securely hold the fin on your foot. The original Oceanic spring-straps, which are no longer being manufactured, are shown below along with some aftermarket spring-straps you can get through Extreme Exposure or H2O Adventure Gear. Note that both stores are chronically out of stock, so order the straps well ahead of when you'll need them.
Below are some pictures of the best way to rig your fins.