Just once after the end of each season, there should be a single create a champ contest.
1. Riot starts by putting out a blank form for everything that you will need. This can be accessed by the main page, and is only the skeleton for how your entree should look.
2. Only players that are level 30 are eligible for entry. There would be a button on the games front page during the week of entry, that would validate your level, and then send you to a secure page for entree.
3. Riot will chose their top 3 entrees. After the top three entrees are in, Riot has a secure page that allows the community to pick one of the three.
4. If Riot feels that there are not enough entrees that belong in League of Legends, they will fill any open entrees themselves.
5. Once a winner is picked, Riot will begin work on the champion. They have the rights to alter abilities so that they are not to OP, or scale them up so the are not under powered.
6. The next season, when the champion releases the contestant will receive the champion for free, with the starter skins, and on the champions bios page the contestant will be recognized.
Explanation for rule 2: I believe that if you are level 30 you have a grasp on how the champions have been played, and if nothing else shown dedication enough to Riot.
All contestants give up rights to their entree once submitted. This will be part of the agreement that every contestant much accept before posting an entree.
This way we have something to look forward to during the beginning of each new season when the seasons are slow as everyone is just trying to gain elo back, Riot gets champion ideas, we get to be all happy they listened to us, and everyone is even more aware of how awesome Riot is.
Feel free to suggest more rules to be added in as those are just the basics.
What do you all think?
Edited to add in SaintPinHead's ideas!