ok so ive been licensed about 4 months now (technician) and there's a local 2m net that runs every tuesday night. ive been listening to it for a few weeks just to get a feel for how it works and i think i mostly understand the format but im not totally sure when its appropriate to just jump in and check in vs when i should wait.

like the net control will say something like "any additional check-ins" and i assume thats when i go? but then sometimes someone will just say their callsign in between other traffic and i cant tell if thats a thing you can do or if they're just being rude. also is it weird to check in if you dont have any traffic? feels like im just wasting airtime saying i have nothing to say lol

anyway any guidance would be appreciated, dont want to step on anyone or make a fool of myself on my first actual transmission

You've basically got the right idea already. When net control says "any additional check-ins" or something similar, yeah that's your window. Just say your callsign nice and clear, phonetics if it's a noisy night, and wait for them to acknowledge you. They'll usually ask if you have traffic or announcements and you can just say "no traffic, checking in" or however the local net does it — they'll let you know if there's a specific format they prefer.

And no, checking in without traffic is completely normal. That's actually kind of the whole point of a lot of these nets — just to make sure everyone's gear is working and people are active. Net control wants to hear from people, that's why they run the thing. Don't worry about wasting airtime, a callsign and "no traffic" takes about 4 seconds.

The person you heard keying up mid-net was probably either late checking in and the NCS acknowledged them, or yeah maybe jumping in at a bad time. Happens. Just listen for a few more weeks and you'll start to feel the rhythm of how your particular net flows, they're all a little different.

same boat as you like 6 months ago haha. honestly just do it, the worst that happens is net control politely corrects you and everyone forgets about it in 30 seconds. i was so nervous my first check-in i forgot to give my name and the net control guy just said "and your name?" and we moved on, no big deal at all