Drywall is one of those things that looks so simple when someone else is doing it...and it can be for you too, if you're armed with the right information and have a little patience. Taping an entire house, or even a large room can be a challenge - creating a perfectly smooth finished surface is a bit of an art, and it takes some practice. Our homes take a beating from the weather, kids, pets, and swinging doors - which means almost everyone has a few cracks, minor dents and dings, or even a few holes in our walls - repairing them is a good way to get your feet wet, and is a pretty manageable project for the uninitiated.
If you have minor cracks in your walls, you can scrape them out to create an inverted 'V' with a knife or chisel, and simply fill with pre-mixed compound using a taping knife. This gives the new compound a better chance to bond to the old surface. 2 coats are often required as the first coat will shrink as it dries. After a quick sand, you're ready to prime and paint the repaired areas. For holes, it gets a little more involved. Avoid the temptation to fill the hole with crumpled up newspaper and handfuls of drywall compound - there's an easier way. Cut yourself a square of new drywall that's slightly larger than the damaged area, hold it on the wall and trace the edges onto the wall. Cut out the damaged section, and your new piece should fit perfectly into the hole. Now you'll need a way to secure the new piece of drywall into the existing wall...if you are able to use the existing studs, attach the new piece of drywall using 1 5/8" drywall screws. If the damage is between studs, all is not lost - attach scrap wood across the inside of the opening, being sure to leave enough exposed to attach your new piece of drywall, or pick up a package of drywall clips (they come with screws and instructions!) and secure them around the perimeter of the hole. Insert your new piece of drywall, and screw it in. Now you're ready for the compound...
Using a 5 or 6" taping knife, apply some compound (about 1/8") around and over the patch, being sure to fill the gaps and cover the screws. Apply some paper or fibreglass drywall tape over the joints, and set it into the compound using your taping knife. You'll want to hold your knife at about a 30 degree angle to the wall, and apply enough pressure to smooth out the compound and remove the excess, but not enough to pull the tape off the wall - holding one end of the tape against the wall will help. Be sure to fully cover the exposed tape with a thin coat of compound, smooth it out as best you can, and let it dry completely. If you don't want the patch to be noticeable, you'll need to feather out the edges with 2 or 3 more coats of compound - when each coat has dried, lightly sand it smooth, and apply another thin coat - the trick here is that more thin coats are better than less thick coats. Be careful not to sand too much, or you'll expose the tape and have to start all over again.
If you secure your new piece of drywall well, the worst that can happen is that you'll end up having to apply more compound and try again. A patch typically requires 2 or 3 coats to make it smooth - when you're happy with the finish, prime the area and paint over it. Voila - damage disappeared!