heres the deal:

people will say try diff strains, dont smoke so much, smoke even more! do this that and something else etc.

those things help, but 99% of the time but its all your mindset. ive smoked for many years now and i still feel the paranoia sometimes. actually now when i start to feel it i get thrilled, because it means im about to be real high soon =p
i usually smoke, then get creeped on with the paranoia and stuff about 90 seconds to two minutes after my first drag. five-10 after that and im fully blown.

i think if you're downing too much other stuff along with your ganj, you totally spoil the experience. especially alcohol in excess, yuck. but hey, whatever sinks your sub man.

the OPs problem is his pre smoking anxiety. in the back of your mind you're all 'omg i hope i dont flip out and panic when i smoke in the next thirty seconds' and of course you do flip out because you were thinking about it intensely the entire time you smoked! then it snowballs - you go 'OMG im shaking! OMG can people tell im shaking?! omg my hearts beating fast! OMG am i shaking because my hearts beating fast?!?!' and once you start with that shit its fcking over, you may as well have not smoked to begin with.

you need to change your environment. change who you smoke with, change where you set and whats on the telly, etc.
keep your mind busy too. try taking a walk. you won't get in trouble if you've got nothing on you, so take a damn walk. walk your dog or something. just keep telling yourself that believe it or not and
contrary to whats taking place in your stoned head, everyone passing by has absolutely NO IDEA that youre baked.

after a while, you get good.
i smoke now and go out somewhere with friends and see how long it takes for them to realize im stoned, haha. sometimes they never even realize it, even when im so baked i can barely see.

being stoned is a skill, like juggling. practice.

obligatory edit: don't promote pills here =(