Different surfaces requites different paint. For wooden materials use enamel. There are two types of enamel, one oil based and the other water based. Oil based smells awful and it takes a long while for it to dry and it's a hell cleaning (you need heavy chimcals like Thinner to get it off tools and hands and you can't empty it in the sink) The water based doesn't smell at all, you can clean your tools and hands in water in your sink and the paint dry fast. The good thing about slow drying paint is that the paint floats out better and create a more smooth surface where you can't see the brush strokes. However there are ways to get around this when painting with water based paint as well, for instance you can lower your temperature in your room where your painting, then it drys slower, you can also rise the level of moist in the air, it will slow down the drying process. Some people also say oil baised enamel last longer, but it's poisenous so in Sweden oil paint can't hardly be bought anymore due to new restrictions about the environment.
If you're using a brush, use one with a fine syntetic brush. Don't be cheap, buy a REAL brush. The better brush the better result when you paint. Those two dollar brushes are worthless and you will be displeased with the result. And a real brush can be washed and you can use it again and again, a cheap brush is spent after one use normally. You can also use a roller, this way you don't have to worry about strokes, the surface will become perfectly smooth. There are many types of rollers, but remember the less "fluff" a roller has the smoother surface. The best roller for a smooth wooden surface is one with no fluff at all, it's a plain foam roller.
enamel also have different leves of gloss. The more gloss the easier it will be for you to keep it clean, but also the more glossy the surface is the more it will reflect light.
As for sanding, the glossy surface must be removed before you start painting or else the paint won't get a grip and it will just create drops like water on a plastic surface. How much sanding I can't tell, my coworkers alwasy said you just need a little sanding but i experience myself a little wasn't enough. I guess it depends on previous paint, the glossier the more sanding required. If there are any hole, damaged edges, scratches and such, use a wood putty to fill it in and sand to create a completely smooth surface before you paint. If the previous paint is coming of, you have ro remove as much as you can before painting by sanding or scraping, or else there's a risk the old paint will loose underneath you new coat and everything will fall off.
This might vary on the paint but normally you use a primer paint first (one coat) and then the real paint (two coats). Many people skip the primer wich is a bad idea since the primer and the real paint work together to create a more firm and resistable coat. (which is a very good thing when it comes to furnitures since you're using them) If the furniture is already painted and you don't have to sand it all bare to wood you can skip the primer, primer only works when it's touching the wood surface, not if there's a layer of paint in between.
Gosh, that was long. Hope it helped some.
