playing with penny stocks

I like the idea of ACTC but i dont know too much about SIRI ....as auto sector is doomed for some time.

Here are some of my picks that i am playing with.... AGT, POT ASH
I bought citi when it was at 1.04 and now i am up at 2.85....... should i sell or stay? Predictions are for it to reach $16 by end of summer.