A close friend is transitioning, how can I be supportive?

[ga_girl]

15. Lots of good advice above

I'd add a few items.
1. Realize that this person has most likely been dealing with this their entire life, frequently starting in puberty if not earlier. It's not just obstacles likely to be faced, but it's obstacles faced.
2. Use your friends preferred name and pronouns.
3. Don't assume anything about her plans regarding transition. Medications and surgery are very personal and frankly it's not necessary to talk about unless it's brought up by her.
4. Please watch your terminology. "Tranny" is offensive. "Transgender Woman" is acceptable, but I prefer "transgender".
5. Remember we all make mistakes in life. Relax a little and don't stress about assumed things.