This is a tricky topic. First of all, the best approach is to hire a professional mastering engineer and ask if you can shadow him/her while they master your music.
They'll show/tell you:
1. tricks that you didn't think to do yourself (multiple levels of A/B monitoring and referencing)
2. where you're making mistakes in your recordings
3. how you can improve your mixes
After you get a feel for the process, you can branch out on your own with much better results.
My chain is typically:
1. Subtractive EQ (remove any conflicting frequencies - think lower mids)
2. Moderate compression (-2 to -3 dB of fast gain reduction at the peaks)
3. Slight high end boost (newer releases are bright!)
4. Multiband limiter
5. Secret weapon: DeEsser goes last - focusing on reducing the 6K to 8K sibilance. Those are the ugly peaks that make homemade recordings sound brittle/digital.