How to become more sociable?

I have problems communicating with real people (and I don’t know why) I am not afraid of people but whenever a subject comes up I feel like words and ideas just disappear from my head and I just stand silently, which results in me becoming a non-talkative person so I don’t have many real friends. I do have some e-friends but still, although I talk more than in the real life, I find talking is a hard thing to do.
I don’t wish to become a talk-without-stopping person but I do hope I can become more open. Can anybody provide me with solutions? All ideas and opinions are welcome (with little sarcasm)
Thank you in advance