As for feeling paranoid while high, I've found it helps to have someone there who you have some kind of respect for, that is also high, but not paranoid.
When I first got my ex to start smoking, we got blazed and went to a 24-hour restaurant at around 2 or 3am. She started getting nervous and kept worrying about the staff at the restaurant calling the cops on us. Being high puts you in a less rational state of mind sometimes, especially if you're not used to it. It really really helps to have someone calmly explain the reality of the situation. She was getting to the point of crying until I explained that, from experience, that doesn't happen unless you're being a nuisance to them, and the waiter could just as likely be high too XD If someone did actually call the cops, what the fuck would they say? "There are two friendly people behaving perfectly normal who may or may not be high on marijuana eating quietly at my restaurant! PLEASE SEND HELP IMMEDIATELY!!" The police wouldn't give two shits. After my explanation she felt totally comfortable and we both happily pigged the fuck out. THE END.
The fact is: unless you're being an idiot and taking stupid risks, the cops won't get involved. And if they happen to get involved when you have been playing it safe, as long as you don't smell like it, don't have anything on you and don't act like a dumbass, there's nothing they can do to you. Those are the cops I'm used to though; I know they can be assholes sometimes, but without reasonable suspicion, they don't have many options.
Paranoia and fear is reasonable if you're high while also involved in something else illegal, but that's just retarded in general. I'm not saying I abide every law, but I've been smoking all day every day for the past two years, and semi-frequently for two years before that, so I am comfortable being high in most situations. But what helped me any time I started losing my calm while high in public situations, I just pretended that everyone else was high too. That and just pay attention to the facts and logic at hand, but also don't just throw caution to the wind. There's a big difference between being paranoid and being cautious.
Your paranoia could also be coming from how much you smoke. I've gotten to the point where I was so high that I questioned whether or not everything I was doing or saying was making me look like a total dipshit. It's really unsettling, but if that's the case, try smoking less, or just spacing it out. Make sure to be there for yourself if no one else is there to talk you down from it.
