1. Make sure there is ventilation space around the case, especially if you are using the internal amplifier
2. Make sure it is mounted solid and not just hanging off a front flange or something. Add a rear strap to it if the front mounts do not have attachment points at least 1/3 of the way back on the sides.
3. Check your depth of the space versus head unit first.
4. Check your angle of the face plate for sun reflection issues and try to adjust if necessary. It's more fun when you can read the display in the sun. Yes, I guess I am a poet.