Below is a table of suggested uses, but do not take this as gospel and feel free to experiment. Some Mic choices come down to personal preference (most rock vocalists will either specify or be happy to use a Shure SM58), some to expediency (if there is no room in the band pit for mic stands, use the AKG micromics), and some to budget.
Other than that, use your ears. Also, make sure that you position the mic to capture the best sound you can. The correct mic position on an instrument can be critical, and can make the difference in acheiving a good sound or a great sound. Also remember, that if an instrument or voice is producing a poor sound, your chosen mic won't make it any better.