Not the biggest tips of all time but you can save a decent amount of money painting yourself.
1. If you pick a higher quality paint through Sherwin-Williams you can setup a contractor account first and save upwards of 20-25% off, or wait for a sale.
2. Medium to high grade tiers of paint have better coverage, as in you do not have to do two or three layers for a clean finish like cheaper Home Depot paint, lesson learned.
3. Always put primer paint on surfaces that are a noticeable color difference from the new paint you want or you believe will not take the paint well or evenly.
4. Surprise tip for darker colors. Primer paint is normally white, but you can have your paint guys actually mix it to a closer shade to the color you want, to really make that cocoa brown or whatever really pop and show that true color well!
5. Also, always paint the ceiling first. Ceiling painter acts more watery and WILL splatter/sprinkle around and show up on walls, at least some of the cheaper ones I have worked with. That or just make sure to prep well. 90% prep, 10% painting seems to be the deal.
Good luck!