Apparently 2007 is better however here are some tips that have worked for me with 2006.
Keep your feature lines simple. A sharp corner in a basin/pond may look like crap on paper but the contractor will get the idea. I have had luck creating a feature line with a circle/arc, then exploding, then turning back into a feature. Not sure what the program is doing there but its worked. I have had luck using multiple grading groups for a single area of a development, like building pads.... make a group for the front, side and back of the building, if your interested in volumes (ie. cut and fill numbers) this method deosn't help you but it works. I have also found that if you wait until you are finished with your gradings before you create a surface the program is more stable. I have also found that after you have created a surface your satisified with it, lock it.... and try not to breath on it too hard...
Grading infills... Don't do too many at a time.
If your creating gradings and then deleting them... or when they dissapear and your trying to go back to a good starting point use your drawing audit. It finds them, I guess in some database, and removes them from the group.
super cool stuff it just takes patience and manager not breathing down your neck for billable time.
DOH, just noticed your on 2007, I need a vacation