You can also anticipate the upcoming chord by using a note from the new chord that isn't in the old one. Like the change from Am-Em you could work in an F#. Those chords are pretty closely related so there aren't many notes of that description. It's a bit of musical sudoku.I'm playing along to a backing track, and simply playing roots as 8th notes.
C - Am - Em
) even the use of F note with those chords.