Some more mistakes to avoid when drywalling.
Applying too much mud at one time. As thick layers of mud dry, they crack. You can fill the cracks, but it adds to your work.
Applying too much mud, period. The trick to successful drywalling is applying enough mud to cover the seam and leave a flat plane (in the case of a joint on the tapered edges) or a very slight, and wide bulge (in the case of a butt joint on the flat edges.) It’s an art which takes some practice, but too much mud simply means more sanding and more mess.
Applying too little mud. The opposite of too much, caused by scraping off everything you’ve put on or not applying enough in the first place. On the tapered edges, this would mean leaving too little in the seam, so a depression along the seam occurs. On a butt joint, this might mean applying a narrow coat of compound which shows up as a little bump, rather than a broad, barely noticeable hump.
Failing to do a quick inspection between coats. Little globs of dried drywall can cause real hassles if you break them off as you apply a new coat. Scrape these off with the edge of a drywall knife held flat to the wall before mudding.
Failing to clean between sanding and subsequent coats. The dust buildup on the wall will make a mess of your next coat. Use a broom or slightly damp cloth to give the walls a quick wipedown.
Not storing mud properly. Dried mud again. Avoid getting it in your container by scraping down the sides as you go. Before sealing up the container, wipe the sides with a damp rag, and cover the remaining mud with plastic wrap, sitting directly on the mud.