You could use your age as an opener like "Tell me how old I look" and then tell a story how somebody thought you were like 14. It opens set easily and you get to tell your age right away so they will take you more seriously from the beginning.

Im 17.
I almost always have some facial hair design or something, and people normally say that Im 19, but Iv even gotten to the point where people say I looked 21. (I actually bought alcohol without being IDed)

When I am clean shaved, I look like im 15! I'm a pizza delivery driver, and one time this woman asked me if Im old enough to drive!

So basically facial hair makes a huge difference.

Lol. Last weekend I opened a 28 year old HB8,5, didnt expect her to be so old:P But I asked her if she could judge me on my age. She said something like 25 And guess what... I am 21. She was with her BF, he was dancing and she came sitting beside me. So ok. Was good moment for my ego. Number close was at that moment out of the question. But you could say I did some things allrite.

She had judged me on my behaviour and looks I guess. Tho I look a bit used up for someone of my age. Will fix that soon enough tho!

But anyway. If people tell you that u look younger dont be offended. Just ask them by what means they think that. If you have a baby face. Just be happy and alpha about it. If they judge you by your acts, than you should work on that. Nothing to be pissed about...