I just use beef (usually 80/20) italian bread crumbs, finely diced onion, egg and parm cheese. I use the fatty meat as it leaves more flavor in the meatballs, I mix it up, roll it up and bake it on rakes in the oven (so the fat) "falls" below. I usually make huge batches at once and what I am not using for that meal or event, I layer on a cookie sheet, freeze until solid & then dump into large ziploc bags.. this way you can pull out 1 meatball or all of them for the next time you need them.
I have seved them in marina sauce, in BBQ sauce, and sweet & sour style w/ some pineapple chunks mixed in (this is my favorite version) and w/ a gravy (brown)