When upcycling furniture, there are a few important steps that have to be taken to ensure a good piece of furniture in the end.
Washing your furniture with a damp rag and gentle dish soap ensures the paint will stick! Dust, oil and even water can deter the best of primers, so wash away!
I can't stress this enough. If you don't prime, the odds are your paint won't stick! Talk about raggedy edges. Primer can be expensive, but it goes a long way. Even the thinnest of coats will do wonders for your furniture, not to mention add a little detail of you're planning to sand and antique your piece.
I highly recommend Zinsser Zero Primer (eco-friendly and safe) - $18
If you can, it's best to spray the paint onto your furniture. This gives a professional, clean coat, and to top it off you use less paint! Over time, the cost of an HVLP sprayer will pay for itself in paint alone. They run for about $150. You can also use spray paint, and some out there even have the primer included - two steps in one!
If you can't spray, try using a sponge brush or a high quality paint brush and brush WITH THE GRAIN OF THE WOOD!!! And never paint in the sun, makes the finish gloppy.