I only assign extra credit at a few points during the quarter, and that's it. Students either decide to do it, or not, but may not ask for extra credit as it gets towards the end of the quarter and their grade needs help. It's a bit of a gamble for them...
I also only try to assign extra credit that will not require me to go digging for a key, and doing more work on my part. So, I come up with activities that the kids might like to do, and I also put in the assignment that kids can earn up to a certain amount of points... For the activities that I use, check this out.
I then assign the activities, and give the kids 2-3 weeks before the extra credit is due.
Once the extra credit gets turned in, I pull out my extra credit tickets:
|I do not know why this picture is sideways... blogger has hiccups right now...|
Then, I look through each assignment (at this point, it doesn't matter if they're all doing different things, because you're only reviewing it for effort and comprehension) and assign a particular number of points onto a ticket. The student then must KEEP the ticket and cash in the ticket when they feel their grade needs the help. If the ticket is lost, so is the points (which teaches total responsibility). I also assign an expiration date for the ticket (sometimes there is no expiration date) as well as a subject it must be used in (or ANY if the work was that outstanding. To check out the extra credit ticket, check this out.