Every week or so, add something new and do it properly. If you can't do it properly in time, don't add it in until it's ready.
Don't add new features into the game until the previous ones are polished enough to be considered releasable. If you're still working on fixing something, don't worry about it; we still want to try it out.
We don't mind if it's a little buggy, so long as we can play it. Polish comes in time. We want to see new features! :D
Release whatever unfinished mess you have at the time as often as you can. We don't mind the constant downloading and we know it's in early alpha so we won't judge. ;)