Okee okee idk if I'm late to this but here's some tips I use!
I was a soprano in choir so idk if this'll apply to you, but its still good practice!
When hitting higher notes, try not to sing "with your head" IF you feel buzzing on the top of your mouth or feel it in your head, your using your throat, possibly straining it. Instead, push out the note with your chest. Basically to test how It feels just do a vocal sigh using your diaphragm and lungs. (If you're doing it right, you should feel it in your chest/lungs NOT your head or throat!)
Now in general terms, Posture is IMPORTANT! Don't slump! also try not to be too stiff. Especially if hitting higher notes. Instead, Just lean your shoulder back comfortably, And make sure to breathe! Use that Diaphragm! Small gesturing movements can help guide your voice as well! (Swaying, hand movements, kinda like acting but not)