I love canning - I can everything from pickled asparagus to my own BBQ sauce.
When you're canning with the product fully submerged, it's called the boiling water bath method. Not tightening the bands all the way allows the air to escape the jars so when they cool, the vacuum pulls the lid in causing the little button to invert.
When you can properly and the jars are all sitting fresh from the water bath on a clean dish towel, you should hear a series of "pops." This is the vacuum being completed. To "test" whether or not your canning was successful, run your finger over the top of the lid and if the button is NOT pointed down, you need to re-process.
Several great resources: The Joy Of Cooking
before the newest revision; an out of print book I highly recommend you seek out, Putting Food By
is like an encyclopaedia of canning (try www.half.com
or other used book website); and anything published by the Ball Jar people - the manufacturer is called Jarden. Here's their website.
For T-Giving - try canning a jam of Cranberry and Orange Relish. It's a no-brainer because no pectin is used - a good novice canning product.