Good Morning, mporte012,

"Any way that works for you." is the simplest answer. A brighty-lit white wall or piece of white paper as background works well for me. Lightboxes with translucent plastic lit from within are available, but not really necessary. Judging the negative quality is mostly just a matter of experience. It won't take long, assuming that you regularly print some of your negatives, to be able to tell whether a negative is worth printing and approximately how easy or difficult it will be to get a good print from it.