How to be a femme ally?
Don't assume we fuck men.
Don't look surprised if we get offended if you assume we fuck men.
Try to look past the hair/nails/shoes/dress/frills/whatever and realise from the outset that while she may not have the ''look'' you expect, you may still be looking at a woman
who is just as (or more*) lesbian than you.
If you're a fellow femme, don't ask her to lend you her clothes if you don't intend to give them back
*'more' is a judgement to be sure, but when you've had absolute certainty about your lesbianism for 15+ years and you may even be a gold star (I'm not) it's really offensive for some 20-something lesbian (or man) to assume you're about to run off with the first bio-guy who clicks his finger at you.