so ive been licensed for about 4 months now and i notice some guys on the local repeater use phonetics every single time they say their callsign and others never use them at all. like one guy says his call completely normally and everyone seems to understand fine but then another guy spells out every single letter with NATO phonetics even when conditions are totally clear. is there some rule about this or is it just personal preference? i dont want to sound dumb on air by doing it wrong either way

There's no hard rule that says you have to use phonetics every single time, at least not in the US on most bands. The idea behind them is just that certain letters sound almost identical over a noisy signal — B and D and E and V all kind of smear together when there's QRM or weak signal, so saying Bravo Delta Echo Victor makes it unambiguous. On a local repeater with good audio and people who already know your call, honestly you could just say your call normally and it's fine. Where it really matters is HF, especially DX contacts, or any kind of formal net where you want zero chance of confusion. Emergency comms guys tend to be pretty strict about it too because in a real situation you really don't want someone writing down the wrong callsign or name or whatever. So basically just use your judgment — if conditions are rough or you're working someone who doesn't know your call, phonetics are your friend.

yeah i asked almost this exact same question when i got my ticket lol. what i found is that on HF it becomes second nature pretty fast because you actually need it. tried to give my call without phonetics once during a pileup and the DX station just came back with a completely different call that sounded nothing like mine so. lesson learned. on the repeater though half the old timers around here never bother and everyone knows who they are anyway so it doesn't really matter i guess