I find that the best way to write a lemon (smut) is by watching porn equivalent to the idea of what you want to write. If your characters are magic users, have them use that magic somehow. If they're empaths/psychic, have them connect on a baser, deeply emotional level.
You shouldn't ever copy paste every scene from the porn to the smut itself, but use it as a referrence. Also, like others have mentioned, it really helps if you yourself are horny while writing~.
If the characters involved have some special characteristics, like persay, a burn scar, have their partner do something sexy with that scar like kissing all over its length. (you can do this with pretty much every scar)
Much the same way, if your characters have some kind of emotional quirk, make good use of it.
P.S - If you find a scene you wrote as cringy or something that the character itself would find extremely embarrassing after the deed was done, that means you're doing something right. Please note that embarassment in this case does not equal regret, but a form of feeling connected to the trust they have for their partner. If you can manage to showcase this, the scene will end up feeling much more 'real'.
