Paul White (the editor of Sound On Sound) gives us the A Concise Guide to Compression and Limiting, a great introduction to the subject.
When it comes to individual tracks, it is pretty much routine to compress vocals, bass guitars, acoustic guitars and occasionally electric guitars, though overdriven guitar sounds tend to be self compressing anyway! The most important of these to get right is the lead vocal, because even modest dips in level can make the Iyrics difficult to hear over the backing.
The article is ten years old, so it deals with hardware compressors rather than plugins, which were essentially unheard of in 1996. But the principles of dynamics control haven’t changed, so the article is still relevant.
He also offers a handy chart of useful compressor settings. While the chart obviously can’t replace the judgement of your ears, it’s a good starting point for novices who find themselves preplexed by the possible combinations of attack, release, and threshold.