Re-Read what you just typed. You dont talk, dont smile, speak with a low voice. All that can be corrected. You can do it all yourself ! You just have to be positive.
Now you want to know how to be fun. Well thats a little difficult. I'd have to say that comes with your surroundings. Are you in college, do you have roommates, do you have other friends ? If you don't watch tv, have no friends, and/or don't go out much, how do you expect to joke around ? Its your environment that influences you.
Now you say, yah, i have all that. I just can't initiate jokes, or be a funny guy. My way of joking around and having a good time with my guy friends is as follows: I make sure I'm the dominant / confident one in the group.
A) This allows me to make fun (in a joking way of course) of my other friends, and get the others to laugh
B) You already have their respect, so something you say will automatically be funnier than if the soft-spoken AFC said it.
What to say to be funny now.......Well, usually I make fun of my friends flaws. One of my friends is goofy, and doesnt get girls. I usually tease him about that. Or you can say something outrageous that gets laugh, for example: I was watching survivor tonight with my roommmates, and the particpant named Eliza was on, i said "ya know, she's so goddamn bony it just makes me want to f*ck her in the a$$.
That comment is outrageous and hilarious b/c it really makes no sense and you wouldnt expect something like that. Now you're prolly not going to say something like that around a girl you just met, but you catch the drift.
Being funny with women is a whole lot simplier than with guys. You dont need to be the funny man. Just tease them about something. Figure out one of their flaws and mess with them. A girl that I was hitting on last week was an English major, so i made sure to rub it in her face that she was 'out in space like the typical english major', but I kept reminding her of it. Another example was when I met a friends sister and she was an HB 9.5. I made sure to tease her about how closely she resembles her brother, and that i didnt know how she got guys when she looks so much like him.
Its stuff like this that makes you a funny guy. Its not necessarily your material though. Don't get me wrong. Its more of how you present it. Granted you can't say something retarded, but something presented very well with less humor is going to be a hell of a lot better than something presented poorly that includes a lot of humor.