We are a sophomore team that spent a day (and a night) last year drilling out our aluminum frame to meet weight. A ziptie would have put us over.
This year, we started weight engineering from the very start. We substituted laminated wooden parts for aluminum in some places where we needed extra stiffness, and generally tried to keep things simple. Our robot is basically a rectangular pizza box with a tower sticking up on one end.
The first time we took the tower, arm, and chassis components to the scales, complete with all electronics and pneumatics, we came up at about 95 pounds. By the time we actually fastened everything together, it was around 105. We held off adding bumpers until we knew the preliminary weight, so we then built wooden bumpers that were designed to weigh about 10 pounds. Our final weight (right now) is about 118 pounds after a last-second addition of some extra "shielding" over our electronics after seeing team 492's 18-inch-long pointed aluminum spear they use to lift tetras.
The best way to meet weight is to think about it at every step of design and construction, and then weigh and tabulate components frequently. I also suggest shooting for a really low weight (our target was 100 pounds) so that when you inevitably start adding features, it will still keep you under the real limit.
One of the 'bots at the PNW practice tourney was 16 pounds overweight.
We really feel for them. Been there, done that.
