I've just found this thread so I'll play a little catchup.
Friday: That if you buy a used bike you should check everything thoroughly after you've got it home. Even if everything you do check is ok, there
will be a problem with anything you don't check.
I didn't check the back tyre thoroughly enough on my new-to-me MTB because I was going to strip and re-grease the hub, and tighten a few spokes, after getting a freewheel remover and nipple wrench. Turns out the side-walls were too far gone (great tread though). Bought a few parts including a puncture repair kit (knowing that if I already had one the rubber solution would have dried up while languishing in a garden shed for years). Walked home.
There was a seriously muddy stretch on the shortest route home. Learned that flat tyres fill up with mud and water. Cleaning that out can wash/brush away evidence of what caused the puncture making it difficult to find the damage to the tyre.
Saturday: Relearned how to fix a punctured inner tube. Also learned that rubber solution doesn't always dry up while languishing in a garden shed for years. Now have (hopefully) far too many patches.
Sunday: Learned about a bike parts/tools supplier who seems to have everything at a reasonable price. Cheaper than Hal****'s, and certainly cheaper than the dealers around me who seem to think that cycling is a rich man's game and no-one could possibly be capable of maintaining their own bike (or want to, for that matter). Parts and tools ordered.