Paranoid thinking is one of my biggest issues, so I'm not sure exactly how good of advice I have, but I wanted to write to say I definitely relate.
Like the above replies mention, one of the biggest things that help me are "checking out" the thoughts somewhere outside of myself -- when it can still be appropriate to the situation, the ideal is for me to talk about it/check it out with the person I am having the thoughts or worries about. But since that isn't always a possibility, talking about it/checking it out with another person outside of the situation can also help (in some ways, perhaps moreso). & If there isn't another person to check in with, then writing it out somewhere also can work -- seeing it written/typed out sort of detaches it enough that it's easier to look at sometimes. (If you've read stuff on or have been in CBT-type therapy, the challenge thought & replace thought type of exercises could fit in well with writing the thoughts out... I think I saw a post in the sourcebook on this here actually.) I've never tried it but I like the idea posted of "tracking" it too.
When the paranoia is adding to my urges or making me feel unsafe, for me the best thing is to distract myself as much as I can until the thoughts subside a bit or until the urges subside a bit -- and then work on the thoughts. If I'm working on the thoughts on my own, I try to feel as safe as possible first before doing so... whatever skills & things make you feel safest (for me it's distractions) are good to have available when working on the thoughts or just when you notice the thoughts are there.
With some of the paranoia when this can fit in with the situation or thoughts, what helps is to try to just hold off on those thoughts or on acting because of them for a set time -- like the idea used for SI of "I will stay safe for *such & such amount of time* & then check in with the urges again," I'll use the same thing for the paranoia... (an example would be if I'm irrationally worried about someone & asking how they are too often, I will use that challenge of not asking them that question for however long, and then check in again, etc etc...).
With things relating to people & new friends or new situations, I definitely find helpful for coping is to try to have things around (either tangible things or just visualization) that are familiar & comforting already, or things that remind me of a time that I felt confident/happy/safe.
I hope at least some of this made sense.
Take care...
