Canning is just one step beyond cooking.
Before you can, you may want to refresh yourself on basic canning procedures. Ball Blue Books are less than $10 and give a good overview of the basics.
Home Canning – Getting a good seal
There are a couple of areas of the home canning process that give new and even experienced canners seal failures if the procedure isn’t followed. You may skip or fudge on these procedures and still get a good seal, but if you follow them carefully, you will not have many failures at all. Remember, unsealed jars should be used immediately or refrigerated and used fairly quickly.
Headspace is the space in the jar between the food and the inside of the lid. The general rule is 1” headspace for low acid foods that are pressure canned, like vegetables and meats; ½” headspace for fruits and tomatoes in the boiling water bath canner, and ¼” for juices, jams, jellies, pickles and relishes in the boiling water bath canner. If you don’t allow enough headspace, there may not be enough room for a vacuum to form, and food may boil out of the jars as well, causing the seal to fail. I keep a 6" ruler with my canning supplies.
Removing air bubbles
Air bubbles must be removed, using a skewer, wooden chopstick or a plastic picnic knife. Don’t use a metal tool, as it may scratch and weaken the glass jar. Even though you may not be able to see the bubbles, they must be removed from between pieces of the food.
Cleaning jar rims
The rim of the jar must be clean. I use very hot water on a paper towel, turning it to a clean spot often, and if I am canning meat, I use vinegar to cut any fat that might be on the rim preventing a good seal.
Preparing the lids
New boxes of Ball lids are now not recommending heating the lids in simmering water 10 minutes before using. I would do whatever your particular lids call for on the box in the way of preparation, as older lids may still need the older procedure.
Extra precautions with a pressure canner:
Allowing enough time to exhaust your pressure canner
I have had my canner "burp" after I have been getting what I thought was a steady flow of steam before I put on the petcock or jiggler gauge. Allow the recommended time for exhausting your canner -usually 10 minutes- especially if it is a large one fully loaded.
Adjusting the heat under your canner
It's best to only adjust the heat down on your canner after it has been pressurized; in slow increments until it is maintaining pressure steadily. Moving the heat up and down to try to keep a perfect pressure will cause the liquid to siphon out of the jars and often cause seal failures.
Releasing the pressure prematurely
Let you canner pressure release on it's own; on a big canner fully loaded, that may take as much as an hour. Don't try to cool your canner with water on the outside, or by jiggling the weight.
Do not leave the jars in the closed canner to cool. Many jars like this will look sealed but fail later, and the food may spoil. Do not tighten the lids (if you are using Tattler type lids, follow the manufacturer's directions.) Allow the jars to cool, untouched for 12 to 24 hours.
Check your recipe for correct head space and processing method and time.