Here are my tips:

1) Do a google seach and find the biggest school districts in these markets. Then find the school calender and find the weeks for Winter break (in February in NE markets) and Spring break (In April in NE markets). Book flights on the Friday/Saturday at the start of the break and Saturday/Sunday at the end of the break.

2) Do a google search and find the convention centers for your areas. Usually the convention centers (or visitors centers) will list the biggest events for the market and the number of attendees. Book trips around these dates. My feeling is the no-show factor for conventions is lower, so the chances of getting bumped on sold out flights increases.

3) Go to ticket broker web page (do a google seach for something like "super bowl tickets") that lists key sporting dates (like college bowl games, nascar races, all-star games) and book trips around these dates.

Just some ideas that have worked for me ..

Happydad