All of the canning tips I know have been covered by the posts above. There is one more thing you can do. After you have finished processing under pressure and have taken the jars out to cool listen for the snaps indicating that the lids are sealing. After 10 - 15 minutes out of the canner all jars that are going to seal usually have. Check the lids to see that they have all pulled down in a convex shape - also use the "tap test" on lids - if they sound hollow and give at the pressure of your finger they are probably not going to seal. At this point re-tighten the seal rings and turn the jar upside on the counter (lid down) and leave overnight to cool. You will be surprised how many dud jars like this end up sealing.