There are a few principles I follow, based upon my reading of the University of Georgia's amazing site, The National Center for Home Food Preservation.
I send that site to anyone canning their harvest for the first time.
This post is short because any advice I can give pales next to that. I will add the following ideas for those determined to use Granny's yellowed index cards:
- The science of food preservation has come a long way in the past few decades. See if you can adapt granny's recipe to modern techniques. That probably means adding lemon juice or citric acid.
- Modern tomato varieties are not as acidic as they once were, so you will have to add lemon juice or citric acid.
- No one I know recommends canning in any containers larger than a quart. Save granny's old half-gallon Ball jars for dried herbs or beans.
- Try to use canned goods in a year, maybe two. I have figs in honey that I still trust ten years on, but honey is a perfect antibacterial. I'd not use tomatoes or pickles after that many years!
- No matter how Granny canned, if the site I've listed says "pressure cooker" go with that. Don't go with a boiling-water-bath technique unless the U Georgia site gives you a thumbs-up.