When you get the lead break - play the tune to the verse or chorus - the melody. Most forgo that for one reason or the other and improvise using scale or mode notes. The chord and the melody should share some of the same notes - SOME OF THE SAME NOTES - when that happens the chord and the melody being played at that moment will harmonize and sound good. So... Pentatonic notes over the chord change ---
http://www.looknohands.com/chordhous.../index_rb.html. C Chord, C major pentatonic will have three chord tones and two safe passing notes. Make a melodic phrase from those 5 notes. When the chord changes you've got another batch of 5 notes to create a new melodic phrase from.
Want to take it a little farther than that hook the melody to the lyrics - if your song has lyrics. That same C chord is being played and the lyrics over that chord are "Now is the time" Your pentatonic notes are C D E G A. I like:
C.....E..F.....G
Now is the time --- C, E, G, A fits as does low A, C, D, E, however it begs the Am chord. I just like C, E, F, G better. Your Improv do what you think best.
The F is not part of the pentatonic scale, however it is part of the C major scale and as it is only in play a short time it's looked upon as a passing note. If you want to hook lyrics to melody notes there is at least one melody note for each lyric word -- Lit-tle and Ma-ry would get two melody notes.
That's the basics - sing the lyrics, under your breath - helps with phrasing. A string of notes is noise IMO, gotta let the melody breath. Grab the pentatonic scale and just play the good notes - LOL. Go have fun.