This seems pretty simple that most people know this, but it’s really worth a discussion. When some singers sing they can really hit certain consonants very hard. The ones to watch for are “b” “p” “th” etc. When those consonants are hit hard there will be a big bunch of air that rushes to the mic capsule and causes a pop. Some singers are better at not doing this than others, but you as the engineer need to put a pop filter in place to help that not to happen.
You can buy a pop filter, be it a metal one or one with a nylon mesh. You can even make them yourself with a needlepoint ring and pantyhose. By the way, if you do that, please use an unused pair. A good friend of mine once had an engineer in his home studio make one with a pair of his wife’s used pantyhose. My friend was about to sing, approached the mic, breathed in, and as he said, “Got a big whiff of foot” and almost gagged on the spot!
If you’re mixing and find a pop, you can used a filter at the offending spot and write over it with a high pass filter. Audiosuite in PT is a good way to deal with it. Put the filter at the point where the pop is gone and write over the file. Leave some space on either side to do a crossfade.