Weight Saving Techniques

[Orion.DeYoe]

I spend a good portion of my free time CADing robots and different mechanisms. The issue I constantly run into is that I get really close to the weight limit before I've added fasteners or any of the other small things that add up to a large amount of weight (rivets, wires, fasteners, spacers, adhesives, decorations, electronics, roller chain, etc.).
So my question to you is:
What techniques do you use to keep weight out of your design? What high-weight situations do you avoid? What materials do you use to get the strength you need without putting your robot overweight.
Please note that I'm not asking how to use a hole saw on practice day at a competition (been there, done that), I want to know how you keep weight out of the design during the CAD and design phase.
For those of you who have experience with high-functioning robots/teams, is having an overweight robot a problem you face regularly? Or are you able to keep everything under 120 pounds from the beginning?