how do i correctly group notes in music?

Answer 1

If it's a simple time (4/4, 3/4, 2/4 etc) then the notes beams are grouped in either 2s or 4s (usually in 4s in 4/4 or 3/4, unless there are only two of course, and 2s in 2/4)

If it's compound time (6/8, 9/8 etc) then groups of three. This is because each beat is a dotted crotchet/quarter note, which is 3 quavers/eigth notes.

If it's complex time (5/4 etc) then it's usually up to you; it depends on the phrasing whether you want it to be 3 and 2 or 2 and 3.