The invention of drywall made the process of renovation much easier, putting up eight foot sections of a wall at a time makes for easier projects and less work, but if youre just trying to fix holes and re-finish -- then you must look into some other techniques.
Refinishing plaster can be a tricky process since it is all tied together to create a cohesive structure. In some cases, the plaster may start to pull away from the support structure. The best way to re-finish a plaster wall is to first clean it of all debris. This might sound simple, but some walls collect years of dust that can find ways into small cracks and groves in the wall. If the wall is not properly clean, then this dirt can cause blemishes when you put a final coat (of paint) on the wall. So broom sweep the wall, scrub it lightly with a damp cloth, and then wipe it down with a dry towel. Use soap and water if necessary to remove dirt, grime, or grease, but in most cases a damp cloth will work.
Next use spackle to fill in any small holes or cracks that have formed in the wall. Many old houses settle over the years and this will make stress factures that cause blemishes in the wall. Use a lightweight spackle and put on very thin coats at a time. Dont be afraid to go too light, you can always go back and apply another coat. In fact the best way to apply spackle is to apply thin layers at a time and then go back and apply it again.
After the thin layers are applied you will then lightly sand the walls. Use a 220 sand paper and see if that is taking the excess spackle off the walls. Lightly sand and do not apply pressure. If the walls are spackled correctly you will not have to sand very much. After that sanding, wipe down the wall with a damp cloth and your now almost done.
You want to add a layer of primer before you paint. This will smooth out any color variations in the wall and make for a clean palette to apply paint. After the primer has dried (at least four hours) you can then start to apply your paint. Roll the paint on in varying directions at first. Then after the paint is applied once in various directions, go back over it apply in an up and down method to work in the finish coat. After that make sure your edges are cut in and do any needed touch up.
Finally your wall should look new. If you see any paint runs, try to brush them out before the paint dries; if not you might be painting that wall again. But other than that, you should be happy with your renovated wall.