I'm going to keep it real with you- Prep work for a piece of furniture is commonly known as the least exciting part of the process. With that said, it is absolutely the most important step. Without proper prep work, no matter how well you paint it, if the foundation is not solid (cleaned, sanded, bleed-through blocker, etc.) your beautiful work will not adhere well. If you're refinishing a piece for yourself, so be it. Skimp on the prep. But if you are planning to sell or doing custom work for a client, mark my words- the buyer/client will be coming back to you for their money back. Save yourself from an extremely awkward situation.
When I get a new piece, the first thing I do is wipe it down to clear off any loose dust, dirt, random glitter, paper clips, etc. I also take this time to begin to know the piece. What does it need? Repair work? Deep cleaning? Sanding? Once it's been wiped off and vacuumed out, my next step is to start deep cleaning. I highly recommend Dixie Belle's White Lightning. I've also used TSP solution. It is a great alternative if you are looking for something through your local hardware store.
White Lightening comes in an 8 oz size and is in powder form. TSO comes in liquid form. Each one you mix with water. Instead of mixing each time, I like to mix a batch and keep in a spray bottle. I spray it all over, let it sit for a couple of minutes, and then I start working with a sponge or clean rag to remove all the built-up dirt, grime and even grease. By cleaning your piece REALLY WELL, you can potentially save yourself the trouble from having to "scuff" sand slick surfaces and then have to clean AGAIN. As long as what you're working with isn't too slick, by cleaning with a solvent such as White Lightning, chalk-style paint will adhere well without the need of a primer or sanding.