The waive and set commands can significantly widen out the ability of PBS to award a line. If someone junior to you drops all the default limits built into a vanilla bid group then PBS might be able to award a line to them but not to you. Warning, this can get quite ugly. I stopped using these after I was awarded one such month of flying. The "set" commands probably won't change anything but theoretically they widen the bid group.

WAIVE Min Days Between Work Blocks 1
WAIVE 1 in 7 Day off in Base
WAIVE Double Duty Restriction
WAIVE Duty in consecutive WOCLs
SET Max Length Of Work Blocks to 19 day(s)
SET Max Number Of Work Blocks to 19

Prefbid.com is a great resource. Also, as a learning tool, it's very easy to file a Dispute. Simply say "pilot xyz got an award that I thought should go to me." They will tell you the logic of why it happened. Sometimes it's not your bidding, but some other constraint (carry in, vacation credit). Either way, you'll learn something.