Recently answered a question like this on another forum-
Use the strap to pull down a bit to stabilize the camera when clicking the shutter. Use the magnifier to confirm focus.
To wind the film, push the little button in the middle of the wind button, then LET go and wind. Sorry if this is obvious to everyone, but for some reason I was holding the button in while starting to wind and spacing was very bad until I started simply pushing the button and letting go before winding.
It is very easy to double expose or not expose with the D. Find a habit that makes it clear to you if you need to wind or not, and stick with it. For me, I wind after I click the shutter, always, every time, no matter what. Rolleicords are similar, at least until the last models.
Get a lens hood. Watch for flair. I added flocking to the inside of my D, info here-
http://www.flickr.com/groups/yashica_tlr/discuss/72157622734630140/
The reversed image may be strange at first but just relax. It's actually an effective way of getting you to look at the *image* and not the scenery, if that makes sense. Just stay away from cliff edges and bus stops, until moving the camera doesn't make you slightly dizzy.
Have fun. People react differently to a TLR. You will have every other old man coming up to you saying they used to have a camera like that. For people photography, I think people react differently because you aren't pointing anything at them and you are looking down. When you do engage people, both of you are dong the same thing- staring at this black box, so there's a commonality for both of you, less 'me vs. you.'