The biggest mistake most people make when taping their own walls is trying to make it perfect the first coat. When you are applying the first coat, all you want to do is get the tape on the wall over the seams. Another part of the first coat is filling the screw holes.
The best way to apply the tape for the do it yourself person is to buy a taping banjo. This tool applies the mud to the tape as you pull the tape through it. The tool is about $30:00 dollars, well worth the money! To mix the mud, you should have a mud paddle that fits in a 1/2" drill, it will be in the taping tools section of the hardware store. Other tools you will need are a hock and trowel, 4" plastic mud knife, 6" plastic mud knife, a cross point screw driver in case there are any screws that are not all the way, and a file for keeping the tape cutter on the banjo sharp, and a small ladder or bench.
Use all purpose mud for the first two coats. When mixing mud for the banjo, you want it just a little thicker than pancake badder. Put the tape where it fits on the back, and feed it through the mud bin, pulling the tape to the top of the bin and put the mud in. When you pull the tape it will ride over the mud and apply it to the tape. Make sure you keep the bin full of mud so there isn't any blank places on tape with no mud, this will ensure there is no air bubbles. Using the 4" knife, or the 6", swipe over the top of the tape with the knife angled backwards and squeeze the extra mud out from under the tape, making sure there isn't any globs left on the wall. Let dry completely! While that is drying you can fill screw wholes and any dents in the drywall. You push the mud into the hole and then scrape off any excess to reduce sanding. You also need to get tape on corners, and and apply them. You will need tin snips to cut them with. You have a choice of square corners or round (bull nose). If you use bull nose corners, you will also want to pick up a starter corner for each, it is a plastic piece you put on the bottom that is square, so when you put your base board trim on, you have a square corner to work with. You will use the the role of tape for the inside corners. Pull the tape from the banjo, only as far as you can reach until you get better. Apply these short pieces end to end, down the inside corner until you are within a 1/2" from the floor. Carefully push the tape into the corner using the crease in the tape to guide you. Carefully squeeze out excess mud with the 4" knife.
When the first coat is completely dry you will see that the mud has shrunk into the screw holes and left a dent. You will need to repeat the process on the screw holes and dents until the mud doesn't shrink anymore. The mud on the second coat, over the tape, needs to be a little thicker then the tape coat so it doesn't run off the trowel before you get it to the wall. Load the hock, the hock is a flat square plate with a handle on the bottom. Using the trowel, smear a heavy coat of mud over all the tape, scraping off any excess. Don't try and be to picky yet, you still have one or two coats to go. Let this coat dry completely. It may take a full day or more and you may have to apply heat, and crack a couple of windows open to let out the moister.
Quickly go over the second coat and sand any bumps that may have been missed. On the seems, you go over the same place as you did before and scrape off the excess again. On the butt joints you run your trowel of mud down each side of the last coat to make the joint three trowels wide, this will make the hump disappear. Remove the excess. Don't worry about the little lines from the trowel yet! Let this coat dry. This coat should dry faster.
The fourth coat of mud is called the skim coat. You will use topping mud for this coat. Topping mud is used because it is made to sand easier. When applying this coat you will skim over any imperfections, like those lines that wouldn't go away, and any little air holes. Don't worry about the lines to much with this mud, they will sand easier. Sand lightly with the paper found at the hardware store in the taping tool section. You will find the sanding blocks there also.
You are ready for last step, the texture. Your wall should be smooth enough to paint now. If you are going to texture yourself, you will need a hopper for the mud, and an air compressor. The mud will be just thin enough to run down in the hopper as you spray, practice on a spare piece of drywall or box outside until you are happy with the setting. Increase the air and decrease the tip size will get you smaller texture pattern. Good luck with your project!