I've been kiting 9 years and still learning. Maybe I'm a slow learner.

Get as much time on the water as you can. Ask questions of more advanced kiters as well. I think good kiteboarding is 90% kite flying skills.
Important things to know - Learn to body drag upwind. You will need this skill many, many times. Don't wear a board leash, they are very dangerous.
Learn how to self rescue and when to self rescue.
Learn to relaunch your kite quickly.
Understand the conditions before you go out. If it's straight onshore don't go out untill you can go upwind efficiently. Get to know the tides.
Look what others are flying. If everyones on 7m kites don't put up you 12m.
Don't go out if its too strong for you or you have doubts.
Don't let other newbees or other inexperienced people launch your kite. Ugly things happen when someone sends your kite from an inappropriate position. I would rather self launch than have someone I don't know launch my kite.
Keep your gear in good condition.
You ask "When to release?" Generally, letting go of the bar and sitting in the water if you feel panicked is a good idea. Modern kites quickly relaunch if you dump them. If you find yourself going too fast push the bar out and sit down. A more advanced move is to bear off downwind to take some of the tension off the kite, reestablish your edge and resume on your old tack.
A couple of scary things that can happen on the water.
One of the worst things that can happen on the water is having a stearing line get caught on your harness or other inappropriate object and sending the kite into a spiral. Once the lines twist around themselves several lines depower won't work nor will flagging the kite. At this point you would need to ditch the lot before you hit the beach.
Also, treat the lines with the utmost respect. A line caught around your arm or finger and an out of control kite acts like a running saw. It quickly cuts deep.
That said, worse things happen on the land. Water is the safest place to be. After launching get onto the water quickly. Don't stand around on the beach looking up at your kite. It's a dangerous place to be.
My intention is not to scare you out of kiting but to develop a healthy respect for the tiger you have by the tail.