With a warm, damp towel or cloth, pinch the rim between your fingers and wipe the rims clean. Cleaning the rim, removes any little bits of food that could prevent the lid from sealing to the rim. This is especially important with super gooey foods like jam and peaches. But, always do it with every canning job.
For those who are still a little wary of canning meat, once you've wiped the rims, you can use a cotton swap dipped in alcohol and wipe the rims once more. Not necessary, but some do it.
Ready for the lids!