When soldering electronic parts together, one hand holds the soldering iron and one hand feeds the solder, leaving no hands to hold the parts being soldered. There's a common tool nicknamed a third hand which helps here. The tool has one or two (or three) adjustable alligator clips to hold parts and usually has a magnifying glass to help see the work.
Mine was always a little difficult to use. The clips would fall out of their holders, and the teeth on the clips tended to bite through insulation on wires. I lived with this for years without thinking much about it, but finally fixed it. It took 10 minutes. I should have fixed it years ago.
First, following this advice from Robot Room, I strengthened the base of the clips so they wouldn't fall out. The problem is that there's a screw which clamps down on a flimsy, hollow tube and can easily crush the tube. Solution: fill the hollow tube with metal so it can't be crushed. The article suggested using a brass rod, but I didn't have that so instead I found a bolt which fit, cut it to the right length, and screwed it in.
Second, I put two layers of heatshrink over the teeth so they aren't as sharp. Should help protect wires.
These were both easy fixes. If you have one of these third hand tools, you should take 10 minutes and fix it up!