I've written before about contests. Take a look at previous posts by typing "contests" in the upper left window and search this blog.
In the KAAY top 40 days, contests were a year round day to day programming function.
Often the sales department was called on to find and trade out the prizes.
There were major contests and phone-in smaller contests. There were registrations at sponsors, mail- in and of course phone.
These contests were run regardless of the rating period. Even in those days the rating services would put an asterick on your rating if they felt you ran a contest that artificially inflated your rating.
These contests were in addition the the numerous record "name it and claim it" features.
Even in those days there were professional contest players. This resulted in limitations on how often you could win.
Contests were fun for the listener and the jocks. Everyone enjoyed them except possibly the sales department.
What do you see happening in radio today in the contest area.