http://everydayfeminism.com/2015/03/supporting-trans-person-with-dysphoria/
I've edited it, but the whole article is worth a read. I don't agree with everything in the article, including the beliefs of the author and website in general, but it's a good start. I can agree with putting most of this into practice. I can't get rid of the bold font, sorry.
Most of this is common sense and decency. I have a friend who suffers heavily from mental illness (not related to dysphoria): social anxiety,