i have always sold my bmw's through autotrader.com. there are other good places such as cars.com or roadfly.com. as far as craigs list half of your callers will come from mars or jupiter.....good luck.
I have sold a few cars through autotrader with good success, including an 02 M3 convertible. you will get a bunch of calls from companies trying to help you with your sale or wanting to connect you with buyers so just have to work through those. good luck.