This is longer than I had originally planned... sorry...
Yes there are many online featurettes regarding basic bicycle repair but a lot of in-depth stuff can't be well explained unless you have your hands on it. Terminology can get pretty skewed since there are multiple names for different items and unless you know which item is which it can get pretty confusing. Besides that, once you get greasy hands you won't want to touch your keyboard.
So, here is what I suggest...
1) Tools. Buy these as you need them and buy the best you can find.
- - For most bikes you will need a set of combination wrenches from 7mm to 15mm then 16mm, 18mm, 19mm, 20mm, and 22mm. It would be excellent to get a pedal wrench as well. Buy a good one or you'll end up buying another in very short order;
- - 1/4" drive METRIC socket set with 6-point sockets, with a range from 8mm to 14mm in both standard and deep well and a couple of extensions. You can also get a set of 3/8" drive if you want;
- - Screwdrivers with flat and Phillips heads. You'll need sizes 00, 0, 1,and 2, then a couple of big 'uns as well;
- - Special tools relating to your bike including a freewheel remover, a GOOD chain tool, a chain whip, and a GOOD cable cutter (NOT wire cutter). Also a chain wear tool, a GOOD tire pump and a GOOD set of long handled allen keys with a range from 1.5mm to 10mm. I don't like T-handled allen wrenches because you can't always get them into small areas;
- - A 12" adjustable wrench and a 2 pound hammer is also a good idea along with a set of needle nose pliers, a pair of vice grips, and a good knife and pair of scissors. A torque wrench is essential for some repairs.
You should also have on hand a bunch of shop rags, white lithium grease, various types of chain lube, an inner tube patch kit, and some good degreaser.
Again, purchase tools as you need them unless you are independently wealthy.
There are a few NO-NOs when maintaining bikes...
1) Do NOT use WD40 or any of its bretheren to lubricate a bike. WD40 is not a lube- it is a solvent. You MAY use WD40 for cleaning.
2) Do NOT use grease on a chain or any external moving parts. When you do use grease it should be sufficient to cover the surface... don't gob it on.
3) Do NOT use a high pressure water stream to clean your bike. Sponges, rags, tooth brushes and a bucket of soapy water is always best.
4) Don't bother with truing wheels or spoke maintenance. Novices can wreck what may have been a perfectly good wheel by upsetting balance and tension.
5) Make sure to install the pedal marked "L" on the left side (non-drive side) and the pedal marked "R" on the right side (side with the chain).
6) Be careful when tightening things... do NOT overtighten, and if an item shows a torque rating then use a torque wrench to get it right.
Teaching bike mechanics takes more than a couple of paragraphs in a questions forum. Go to a local shop, ask questions, find kindred spirits at a bike club, look for bike service seminars at local shops.
EDIT- I just got an email regarding the use of cheap tools, particularly "mechanic quality" bicycle tool kits from various bicycle retailers... yes, they are relatively cheap, offering a selection of various tools in a neat little plastic case. These may be OK for the well intentioned bike owner that doesn't mind if a tool breaks or bends every now and then but I would never recommend them. Sorry. Purchasing tools from Park, Eldi, VAR, Bicilogic, Pedros, and other dedicated tool companies will be more expensive but they will work better and last longer. All of these companies have "home mechanic" tools and professional tools.