the key thing is to have a well established approach, and that's much easier if you start it from a known point at a known configuration.
I suppose that works OK at your home airfield but not so good if you fly into somewhere new for you. I find the best way (and this isn't much help I suppose to the OP who I assume is bashing ccts at his own field) is just to do it by mk 1 eyeball. When it looks right then it's right. I don't look at the altimeter once I'm on downwind, in fact if it's a field with a big elevation change then I don't bother with the altimeter at all, I reckon I can judge, or hope I can...
, what a thousand feet looks like.