When I was nervous about my first kiss, I heard a lot of advice along the lines of "don't breath". This terrified me because my lung capacity is kind of low. Anyway, I breath now because why would I not? Just gentle breathing, not panting/hyperventilating. My boyfriend also advised "don't suck" as in... suck on their tongue or lips or whatever. I thought that was weird advice because why would I do that?! But you've asked if you suck their tongue, which is a fair question because how would you know? Don't do that... personally I get nothing at all from that, even when it's more sexual than a regular kiss. It's just a bit weird (to me).
I would also like to reassure you that once the terrifying 'first kiss' is either underway or over with, it's a lot more natural and you won't be so nervous. In saying that, I remember that horrifying video of the couple who saved their first kiss for their wedding and they were maximum tongues so... WHOKNOWS