Doing your own plumbing repairs can save a bundle of cash, but there are all sorts of little things that you might not think of that can send your DIY projects awry. Here are a few mistakes that amateur plumbers often make.
For example, you don't want to use a normal wrench to tighten any fixture that has a chrome finish, because you're inevitably going to scratch the chrome and your brand new sink won't look brand new anymore.
The correct tool to use is a strap wrench, though you might be able to cheat by wrapping the chrome fixture in a towel.
Other mistakes include accidentally deforming old pipes with your wrench (loosen the pipe wrench so that the pipe makes contact with the back of the wrench in addition to the teeth) and using the incorrect length of screws.
How to Avoid Rookie Plumbing Mistakes [This Old House]