1. Take a step back after your mix - leave a gap between the two processes helps avoid ear fatigue.
2. Compare your track to others in a similar genre - A/B'ing might be the most important tip, Listen for stereo width, overall volume, compression levels, prominence of the bass and vocals and so on. If your track sounds flat by comparison use exciters or EQ to liven it up a bit. If it sounds too narrow then apply a little stereo widening, all the while keeping an eye on your levels.
3. Use multiple monitors and headphones - listening on a bad system can reveal issues that aren’t apparent on studio gear.
4. Old Rules don't apply - mastering use to be the louder the better. That is no longer true. You must know the final destination of the audio. Platforms like fm radio, satellite radio, and Spotify add their own final touches. When you master it too loud it may get squished even more.
5. Trust your Judgement - If you think it’s sounding too hot, it probably is. It’s better to be a little less intense than a little too intense.