I weigh myself every day. I don't beat myself up if I'm up a pound, I just wonder what could have caused it, ask myself if my eating was out of control in the last few days, and change my plans accordingly. For the last few weeks, I've been stuck in a plateau. I've only got about 10 pounds to lose before I hit the top end of my goal weight (and can only reasonably lose up to AT MOST another 10 pounds after that).
In addition to weighing, I use a fabric measuring tape to gauge fat loss once a week. Sometimes you won't see any movement on the scale but will see a smaller number on the tape. That happened to me for three weeks - I lost a total of 1.5 inches off my waist in that time, but the scale stayed the same. Obviously, I was building muscle at the same time as losing fat. Bonus.
Another way to gauge progress and strength is how you look in the mirror. I take progress photos once every 4 weeks or so, starting with a "before" photo. Last night I took a photo of my back to see if there's any definition showing yet. There isn't much, but there's definitely a lot of muscle under there. I just need to continue with the cut and I'll be totally ripped. I see small lats, big shoulders, and some decent upper back muscles under there. I'm excited to keep going now that I know that's there! (photo quality sucks, sorry)