Err,
I'm a self taught taper, been working on my house for 4 years, started with the off rooms for practice, then worked my way to living room, hall way, mud room etc. Then I spent some time with an actual taper to get some tips and pointers. Youtube is a great place to start, you can watch the various techniques, and how others complete their joints...
Start with a 6" trowel, put a 1/8" thick patch down your entire joint, put the paper over top and then retrace that joint pushing all the excess mud out. Do this over all your joints (tapered edges first) then do your **** joints, then do the corners. Allow this all to dry. Next day do your tapered edges again, this time use a 14" knife (should have a very slight curve in the blade) go over your tapered edges with a nice consistent application of the mud, this should span past your tapered edges on each side about 3-4 inches - make sure there are no air bubbles in the mud or you will have to sand and apply more. If you get the mud smooth this will be your last coat for the tapered edges (no sanding at all). Make sure the curve on the knife is toward the wall
Now, start on your but joints (there are a couple of ways to do these). After you have let the mud dry under the tape, apply another coat of mud (1/8" or so) a face coat (or something) to the tape with 6" -10" knife - the goal of this is to hide the tape in a nice smooth application without air bubbles or fish eyes (air holes). Once this has dried then you will take a 14" knife again and feather these edges, run a path of mud that meets up with approximately the middle of the "face coat" this will the apply new mud approximately 8" past the face coat and will feather the edge. If you have applied the mud smoothly then you should not need to sand much at all.
The other way to do the **** joints is with a 14" knife run an application of mud up the middle of the **** joint (after the mud under the paper has dried), then apply mud to both sides of that 14" mud path - this is more difficult as you then are required to blend the different knife strokes - I find if I do it this way I have to sand more. I use the first method, takes longer, but less sanding.
Corner joints:
Run your 1/8" this path of mud on either side of the corner - take your paper tape and crease it in the middle (folding it in half). Apply your tape like mentioned above, and work the excess mud out of the tape, leaving the corner nice and true. Let the tape/mud dry.
Follow this up with 6" knife, leaving 1/8" thick path of mud first on one side, then on the other (letting the mud dry between passes) - this is an easier method, I now use a special tool (can't think of the name that applies mud evenly to both sides of the inside corner as you push down the suction rod (previously used to **** mud into the tool). You can also buy inside and outside corner bead (but I find this stuff to be a pain, usually end up with air bubbles and a lot of extra work. If your drywall is clean you will not need this corner bead). Anyway, do one side at a time and this way you will end up with nice clean corners.
Unless you have big "boogers" as a previous poster has mentioned you SHOULD NOT NEED TO SAND, simply re mud over the inconsistencies. The other thing of note is GET THE MUD ON THERE. A lot of new mudders put the mud on then take it off again. requiring a BIZZILLION coats. You should really only need 3-4 at absolute max. Sometimes it takes more, and that's okay.
Mudding is not rocket science, but it is tricky to master the flow of mud/pressure on the knife, and how much to apply. It takes a lot of practice to get good at, and very difficult to learn just on your own. I liked the advice of hiring someone and paying good attention to them, or you could broach the possibility of helping for a smaller fee (although most would want to charge more for "help" from a newbie). If it isn't something you want to learn, and you have the money to outsource it, I would definitely say it is not worth the headache - plus, speaking from experience, at the end of the job ALL YOU WILL SEE IS YOUR FLAWS - and the first job, there will be many.
unless money is really tight, don't cover it up with wallpaper and fudge it...do it right the first time and you wont have to go back to a half assed attempt at making something nice.
The other important bit of info (in my opinion) is avoid the fiber tape like the plague. That stuff is nothing but hassle, it will usually crack in time (if not right away) and often newbies don't apply/sand enough of the mud and the squares come through. I had to redo everything I did originally with the fiber tape again with paper tape. 80 percent of my joints cracked within 1 year. Good practice, but I hated it.
I rambled a lot, but I hope this helps.