Summarize this article in one sentence.
Not every station offers the same contests or prizes. In order to take full advantage of what radio contests have to offer, you have to listen to a bunch of different stations to see what kind of contests they're running. One station could have a call-in contest happening at 2:00 PM, and there may be another contest happening on a different station at 5:00 PM. Once the first contest is over, switch over to the next one and try again. The more contests you try to enter, the better your odds are of winning. If you can, listen to the radio at work, at home, in the car, or even the park.This way you can figure out what each stations' pattern is. See which stations offer more opportunities to win, which have better prizes, and what times the contests run during the day. In order to truly maintain a competitive edge, you have to listen to as many stations as possible and get to know them inside and out. You don't need to have a radio to be able to listen to radio stations. You can pick up stations on iPods, iPads, mp3 players, and your computer. Every station has a website and they usually have sweepstakes or contests you can sign up for on their websites where you don’t have to be listening live to win. Go to the website and register for them. This way, you can bypass the time restrictions of live giveaways and save effort. You can also sign up for their mailing lists for upcoming contests.  Occasionally, you will get extra clues or times e-mailed to you. Check all the radio stations in your area and see who is giving away what prize; you can switch stations during the day.  There are reportedly less contestants who play contests listed on radio station websites which means your chances of winning are higher. Time yourself accordingly to listen for when the call number or song of the day is announced, helping to avoid missing out at the last moment. If you have to call at 9:01 AM, then call at exactly 9:01 AM. You can use your cell phone, computer, cable box, anything that has the exact time. Usually, if a contest is from 6:00 AM to 10:00 AM, they are going to give the signal to call, near the end of the show, to keep you listening as long as possible.

Summary:
Listen to various radio stations. Listen to the radio as much as possible. Research multiple winning avenues. Listen to the rules and clues carefully.