Little Devil says:
If you lack the proper place to do mixdowns or mastering, there are a couple of things you can do.
1. Mixdown then before you master listen to the recording in as many different rooms and sound systems. Use a notepad to take notes. Then re-mixdown using your notes.
2. Fire up a frequency analyzer and watch the spectrum of one of your favorite mastered commercial tracks. Then use that as a guide when setting the levels of the different frequencies making adjustments during mixdown or at the time of mastering.
3. Always remember to put your tracks asside and wait some time after mixing down and mastering.