Safe computer cleaning tips I've collected from various techs:

Don't spin fans with compressed air. You can spin them past their designed speeds and damage them. Hold them still when blowing them out.

A soft round paint brush is great for corners (and keyboards). 1/2 inch or 1 inch work best.

Use puffs of compressed air to dislodge dust and debris. Hard blasts could drive it deeper into where you don't want it.

Vacuums are dangerous to computers, both through suction and possible static. Blow and brush everything out of the computer, and vacuum it up after you've moved the computer out of the cleaning area.