Something meaningful. I guess that is very different from person to person. I know that girls do present such as cosmetics. Boys don't give or get presents. Hahaha
It's really depends on what the pperson like and need to. Could be some books, towels, some character's thing, stationary, mugs, some decoration for a room, funny things, toy and so on.
But for me, when it's friends to friends, often with album(fotos which took together in the past)and messages.
I don't think it's traditional but what is the traditional way is when it's friend (not family member) we don't often ask the person what your wishes as a birthday present because it better be surprised^^
Usually we give what they said before that they want. It's not base on tradition, as i think we don't have the tradition of the gift. And in the friend man to man, usually we don't give present, and just sometimes a birthday man pay drink and snack for his friends.
送给他们喜欢的东西，根据他们的爱好来选择。
I will give something practical or fictional to my friends, such as phone, watch . Etc
And I prefer to receive something practical as well.
No preference.
Normally we will treat the dinner to them.
Regardless of tradition, Just whatever they want or something I want to show my sincerity like letters
Book watch game cd
Not tradition
I don't think the presents are based on tradition.