It's not scientifically proven whether or not all girls can squirt. Some men claim that they can make any girl squirt, other women claim that even the best sex gods can't make them squirt. It's unclear either way, but I'd certainly not give up on it!
I've never made a girl squirt (I've only been with 2 and neither of them was bothered about relaxing and trying to squirt) but I remember watching a semi-porn video explaining how to make a girl squirt. There is basically a specific are INSIDE your vagina that you need to rub to make yourself squirt. Rubbing your clit/having someone give you oral helps to increase your arousal but from what this vid said, there's no way you're going to squirt by that alone. It's kinda hard to explain, but the area that need to be rubbed is basically 'behind' your clit... ish. It can easily be reached with your/someone's middle finger. It feels rough/bumpy, kinda like a scrotum but harder/more solid. You have to rub that in a specific way, and you have to relax completely. I think it would be easier for your first time if it was a guy doing it to you so you could literally just lay back and relax. You will get a feeling like you need to pee and the natural relfex is to hold it back, but this is actually you trying to squirt You have to completely relax all your muscles and allow yourself to pee. You won't actually pee because of where certain valves and tubes are, so you don't need to worry at all about actually peeing on someone lol, just relax and go with the flow (literally lol) and fingers crossed, you'll be squirting in no time!
Hope this helps. Remember the key is to relax, so don't get frustrated if you can't squirt straight away, just have fun trying, and maybe use a few toys too if it doesn't work with your fingers or you don't want to finger yourself. And of course you could just google the video, I think it was called something like "sex 101: how to make a girl cum/squirt".
Have fun ;)