To get a jump clone you need to either have;
- Standings of 8.0 with an NPC corp that has medical bays (not everyone does).
- Your corp has 8.0 standings an NPC corp that has medical bays.
- Docking rights and medical bay rights at a station in null sec. These rights are assigned by an alliance.
A pilot may jump between clone bodies once per 24 hours. That total not once per body. This is a great way to get across large distances quickly. I have a character that is a market seller and she jumps between two different markets and sells in places 28 jumps apart without travelling. People who live in null sec or wormholes often have a jump clone in empire so they can buy skills and equipment easily.
You can't keep all your clones in the one station. It causes issues and you should get an error message if you try. There doesn't need to be a medical bay on the station you have your jump clone though. It can be anywhere. You should also make sure your respawn point (or medical clone) is not on a station you have a jump clone as it causes issues. I'm fairly sure you will get an error message if you try to do this.
Jump clones last until you destroy them. That means you should make them when you are able in case you need them later. They cost nothing to leave in a station and cost less than a million to make. They are a worth while investment as you may find yourself in a war tomorrow and you don't want to risk your +5 implants on a station camp.
There are now new skills that affect jump clones. Advanced Infomorph Psychology adds an extra jump clone per level to a total of 10 clones. Infomorph Synchronizing reduces the cool down period for the next jump by one hour per level allowing you to jump every 19 hours at level 5.