If it is an informal presentation on a topic of your choice...
1) Know your audience. Think about what would interest them to hear. If it's a class, of course your teacher is part of the audience.
2) Be yourself. Pick a topic that you know a lot about and are comfortable with.
3) Tell them what you are going to say, then say it, then tell them what you said.
Some completely random ideas.
a) One way in which the Turkish and English languages are similar, and one way in which they are different.
b) In your favorite band, simply describe the band's instrumentation, musical techniques, and musical styles. Don't talk so much about the emotion, talk about the music itself. Do they use electronic effects or not? Can their music be appreciated live, or is it basically created in a studio? If the group uses a guitar, what kind of guitar is it, and what things have you noticed about the playing technique?
c) Three ways in which the town you grew up in has changed during your lifetime.