The key to any good paint job is the prep work. Half the prep work they try to hassle you into is pretty much worthless. Start with your supplies, once you've picked your paint color, you just need 3 simple items, a cheap paint pan, a roller brush (we used the larger thicker roller because we have textured walls,) and a good edger brush. I recommend a Purdy or TightSpot 2" XL Premium Angle Brush which we picked up at our Sherwin Williams store. If you take a little extra time to be neat, then you can easily avoid the messy drop cloth or the painters tape which seem to be more of hassle then they are worth. Just lay out a garbage bag to keep your bucket of paint and your paint pan on. We painted 3 whole rooms with just these couple of items (Chris laid a small drop cloth down to feel more comfortable about drips.)
Don't forget to spackle those nail holes closed. I did this the night before to give it time to dry, then on paint morning I went through and lightly sanded each hole. You may want to slather a little primmer on these holes to, but unless your going from a very dark to very light color, you can skip the primmer step.
Then have one person tackle the edging (me) and one person come behind with the rolling (the Mr.)
Here is me getting my edge on!
After a day of painting, we transformed 3 rooms into a light, airy modern feel with a little Mindful Grey. (Now to get some furniture in here.)