9 out of 10 bikes I get have missaligned frames. The quality 531 or Columbus frames I take to a shop. The others can be aligned by hand. I typically can align a fork by bending, using the ground as leverage. You want to bend the blade out on the side the wheel is closer to. Then bend the other blade to get spacing correct.
Rear triangle can be aligned in a similar fashion. I use the string technique to eyeball the missalignement. Bend with my hands or by stepping on rear triangle and pulling out stays as necessary.
Best to learn on some cheapo bikes before tackling something nice. Almost all the bikes I worked on at the bike shop I worked at were out of whack. It became general practice to check alignment with a string before doing any work on a bike. Bend it straight and then proceed with repairs. Most of what I was repairing were department store bikes. Bending frames and components was the only way to get them to work well.