I am very good at a lot of different things. There is very little involved in construction and home repair that I am unable to accomplish. I am fairly adept at microelectronic repairs and I am also pretty good at fine woodworking. When it comes to automotive repair however, my abilities are pretty limited - mainly because I have generally found it far more efficient to work trade with mechanics who can get it done more efficiently, while I can get work for them done more efficiently - but I can do the things I am capable of rather well - such as brakes.
The thing is, being capable of many things, I also am very aware of my limitations and I work within that framework. For example, while I am rather capable of certain basic appliance repairs, I don't even consider trying to tackle most of it. When I run into things that are obviously not something I should be mucking with - I don't muck with it. I have immense amounts of experience fixing the muck-ups of other people and I just don't go there. For my own part, if a homeowner made an attempt at a repair and screwed it all up, I would generally charge a little more. Because usually their attempt is going to make the actual repair more difficult for me. The exceptions to that are the folks who stop as soon as they realize that they're in over their head - or the folks who hired someone in good faith who wasn't capable - in which case I usually cut them a break.
Whoever tried to do the brakes on my van, seriously mucked them up. What should have taken me less than two hours and cost about a hundred dollars in parts, took the better part of yesterday and a few hours today - and cost nearly eighty dollars more than it should have. And this isn't the only muck-up of theirs I have had to deal with with this van. There is a lot of evidence of their incompetence.
So I have a few tips for DIYers out there, advice that will save you money, headaches and keep the person who comes along to deal with it if you can't, from being really cranky and charging you a lot of money.
First and foremost - The moment you realize that things are not working out the way they should STOP!!! Do not continue until you have ensured that you are doing it right, or have found clear directions that will move you forward from there. If you cannot make either of those things happen, call someone who can.
Second - If it does not look the way it did when you took it apart, you're probably doing something wrong. Unless you are changing a fixture out for one that is different, it should go back together the same way it came apart.
Third - Bolts do not need to be tightened down so hard that they will never come back off. If there is no specified torque, you should tighten it until you run into resistance and then go about a half to three quarters of a turn further. Over tightening is likely to cause damage either right now, or the next time that nut or bolt needs to be removed (This would be one of the problems I ran into with this brake job).
Fourth - Use like fasteners. Do not try to improvise fasteners, unless you absolutely know what you are doing and what will work instead of the one you took off. If the screw, nail, bolt or other fastening doo-hickey doesn't look like the one you removed - chances are you shouldn't use it. (The reason I had to do the brake job in the first place)
Fifth - Don't be afraid to go to online forums and ask for help. There are forums for virtually everything you could begin to try to repair and they are quite often frequented by pros who, mainly to feed narcissistic tendencies*, are happy to help you figure out what you're doing.
Sixth - If you are working on a car, on something involving wheels - symmetry is usually rather important. If you change one tire, change the one across from it. If you change shocks or struts - again change both. If you are changing brake pads and/or rotors, change the one across (calipers are a different story). If you are not sure if you need to change both sides, ask - the folks at your auto-supply store can probably tell you.
Finally, and I can't stress this enough. If you aren't sure - if something doesn't seem right - STOP!!! Do not continue until you have assured yourself that you are doing it right, or you have found out how to do it right.
* This is one of the motivating factors that drove me to do that sort of thing and trust me, I'm far from unique. Not to say that we're assholes - we genuinely like to help others, but narcissism is definitely a factor.