make "money" flying
I regularly do "self sustaining flying" around holiday times-- For example, around Thanksgiving, I will book a flight (way in advance) for the wednesday before returning the sunday after, but I will pick a starting flight that will have alternate routings available later in the day-- and just sit by the gate waiting for them to ask for volunteers-- worst case, I make it on my first flight-- usual case, I get bumped at least once. Two years ago on UA I got three RT flight vouchers out of $200 trip from LAX to ABQ. Last year, 2x $300 vouchers for a trip from LAX to JAN on CO.
It doesn't take too much thought to know that the key is to pick busy travel days-- holidays, monday mornings, friday afternoons... (although you have to plan far ahead if you want this to be affordable...) and be flexible as far as when you get places. For me the hassle of sitting at the airport for the day, or having to come back the next day, is worth a free trip/ticket-- but i'm a starving grad student.