Shy around girls and shy around guys, if you're telling the truth you really are stumped. Is it just people your own age who you struggle to talk to?
Ask open ended questions. Get the person talking about themselves, or their own experiences. People love talking, even when they're not allowed too, just think, in the classroom there's always somebody getting told to be quiet.
There is no set topic that anyone here can give you that will guarantee you a successfull conversation. The closest I can think of, is asking somebody what they did today. I reckon you should give it a go. When somebody asks how your day has been, tell them, don't just say 'erm, yeah it was ok I guess' let them know what you did with your day. Then ask them if they did anything worthwhile with theirs.
If they say it was ok -
ASK why it was ok.
If they say it was great -
ASK why it was great.
If they say it was bad -
ASK them why it was bad. (Once you get a little better actually talking to women, wean yourself off of this one, we don't want you getting thrown in the friendzone and being her emotional tampon now do we

)
Now I'm going to ask you a question.
What do you like to do?
Once you've thought of something tell me -
WHY do you like it?
There, I just started a conversation with you. Your turn.
Gunner