When building the wheel, work on out of round first. On the rear, once you start getting some tension in the wheel start working on dish and lateral trueness. If you true from only one side of the wheel, the right side indicator for example, and flip the wheel frequently, the dish will take care of itself.
For final tensioning, you can do it by feel, like coyotecrust said. Take a wheel that you know is properly tensioned and feel the tension in the spokes of that wheel and you will have a good guide for the tension of your new wheel.
The last thing I do is stress the wheel. I put the wheel on the floor, balance my self on the edge of a table and put one foot on the rim. With the other foot, I gently push on the other side of the rim until it just starts to flex. Go easy. You will hear lots of pings and pops. Go around the wheel, flip it over and do it on the other side. Put it back in the truing stand and re-tru. Repeat the process until you can stress it and the wheel does not go out of true.
I've used this method and had wheels that have lasted for 15+ years of consistent riding with maybe one or two truings.