Watch the Add a Simple Melody Line online guitar lesson by Vicki Genfan from Acoustic Rhythm Guitar Cookbook
Remember that we're using the p-i-m-a system of labeling your right hand (or picking hand) fingers. Try using the fingers I've suggested at first. Take some time to make sure you're getting a good, clear note when you pull off. Note that for the F chord and C chord you don't need to finger the entire chord. Another good habit to create is to see how many fingers you can keep down when changing chords. Sometimes we take our fingers off only to put them right back down again, where they were. Your very last note can be easy to play – if you plan for it early...try moving your hand position while you're playing the open E (1st string) so you have plenty of time to land on that last note.