My wife and I have painted many many rooms. We work out to be a very good team, as she is better at edging, and I am better at the rolling. But I know nothing about effects, stencilling, etc.
Painting is one of my favorite home jobs, because few other jobs show such dramatic results so quickly, easily, and cheaply.
Prep takes as much time as the actual painting, and is incredibly important. Make sure the walls are clean. Wipe them down with a dry rag, and wash them with plain water. Use a primer like Killz to cover stains, adhesives, etc.
There really is no need for tape. Simply be careful, take your time, and feather your brush.
I personally feel it looks better it you brush the edges first, and then roll. But my dad always argued that you should roll first, and then edge, because you can really get very close to the edges and, therefore, will have to do a smaller area with brush - which of course, is slower.
The more light the better. I have an old floor lamp with 5 bulbs and no shade that I use while painting.
Buy good paint. It is worth the price, both in ease of application, and durability. If you believe more than one coat will be needed - say if you are painting a light color over dark - use a tinted primer first. Primer is much cheaper than paint.
The colors generally tend to show more color on the walls, than on the paint chips. If you get below the 2d or 3d hue on a pain chip, it is going to look pretty dark on the walls. Not to say you shouldn’t use dark hues if that is your choice. But it is generally easier to paint a darker color over light, than vice versa.
If you are uncertain, you can buy a pint or a quart of a color, and slap it up on the walls. Or paint big pieces of cardboard/plywood, and move them around the room at various parts of the day. The same paint can look very different on adjoining walls, and in different daylights or artificial light. We used a mustardy tan - called something or another sand - in our family room. In most lights it was really lovely. Yet under some conditions, it was really mustard yellow. We repainted it with a tan which was the same value, but on a brown instead of yellow base. Most of the time it looks identical to the first color. But it never looks yellow like the other occasionally did.
Bring your pillows, curtains, etc to the paint store. It is easier to find paint to match a bedspread, that the other way around.
For most living rooms, I prefer an eggshell or satin finish. Gloss/semi-gloss is pretty much only for kitchens and baths.
Consider going with a maker’s “themed” collection. Such as one of the Benjamin Moore historical collections. The rooms of your house will flow more seamlessly than if you just mix and match from a variety of palettes.
My personal preference tends towards white, or lighter, ceilings. I think it makes the rooms look larger.
Paint the closets while you are at it. You will be glad you did, and if you don’t do it right away, you never will get around to it later. A clean white closet appears much brighter.
Roll slowly. It greatly cuts down on the splatters.
Perhaps most importantly, don’t crack the first beer until you are done painting and beginning to clean up. 