i had the exact same phobia of not knowing what to say
so heres wat u need to UNDERSTAND:
insecure people often feel that convos must have a "purpose". for instance at school you only feel comfortable talking to a girl at a party if you have something to talk around...EVERY TIME...so every time you try and talk to that girl about something that was in ur bio class together, either something funny or homework....
a lot of PUA might make use of those shared experiences AS AN OPENER and then switch....were an insecure person will think: i dont know what to talk to her about...oh we have bio together...and you cling to that convo.
this is bad. if you cling to one topic it will mean:
A) once that topic runs dry your fucked with nothing left to say
B) shell notice that thats all you two talk about and that will come off as insecure
so heres what you need to DO:
when you go out with friends, you are socially vibing...not clinging to a topic....its not like business meeting where you discuss your one deal and then reconvene to discuss that same deal later....
theres three parts to effectively VIBING:
1. dont try to argue. insecure people will see any convo as an opportunity to DHV and go into attack mode. instead phrase it as a yes is yes and no is maybe: "ya i hear ya, but you understand how books are..... or ya definatly, but u see how one can percieve it....."
your not being walked over, but your not being insecure and arguing and killing the comfort
2. dont reject social ques:
if you have seen superbad! you know exactly what Im talking about! if she says something about wanting to join you one night or hang out or see your soccer game or anything like that....acknowledge it! dont be like the guy in super bad who would be like:
HB: oh you play soccer, ya i thought about going to see a game maybe i will...
GUYFROM SUPERBAD: "...um ya i dunno its hot out and i mean i dont always play the whole game---"
GOOD VIBING here would acknowledge her social ques and say:
"Ya thatd be awesome, i better see a big sign!"
another example of a poor accepting of social ques is this:
BOB: you wont believe what I got this xbox 360 for!
YOU: lemme guess you gotta deal on it and got it for 150.
BOB:...ya...175...howd u know? .....
INSTEAD:
BOB: you wont believe what i got this xbox for!
you: i dunno 600?
bob: nah 175!
you: shit thats sweet! who the hell did you have to kill for it?! haha
instead of trying to intercept and be insecure trying to guess ahead that he got it cheap...just VIBE and GO WITH IT!
3. Body language:
a. if you cant get eye contact (dont be a creep and lock without blink lol) at least keep your head up! look above the horizon especailly when walking
b. be congruent in your speed of movement and talking (err on the relaxed slower side)
c. match their intensity (if they are excited, so are you)...this is differnt when trying to be the life of a party when you go out obviosly
finally heres the biggest tip: you will never be afraid to hold a convo again!
open ended question or statement: pull out a key word and do it again!:
her: bla bla bla bla bla dogs bla bla bla
you: ya i had a dog...his name was ______, u have any pets?
her: ya bla bla bla bla story about her pet bla bla bla uncle and shot guns
you: woa! your uncle collects shotguns!? is he scared of you?
her: NOOO!

...well actually this one time bla bla bla bla bla forest bla bla bla
you: ya forests and me dont sit well, i went camping once,....bla bla
i know your reading this and thinking DUH its called conversation.
but for some of us who arent very socially intelligent like i was, actually need to consciosly pick out key words to constanlty mold the convo.
you will need to callibrate how drastic of a change you need to make with keying certain words and how often, but really u should never ever be afraid of holding a convo once you master how to key certain words and elongate a convo that you once would of stalled.
the point: if your talking about dogs and she mentions her uncle in tazmania...WOA....forget dogs thats your new convo!