Watch the Chord Tone Soloing online guitar lesson by Jeff McErlain from Essentials: Chord Tone Soloing
What is chord tone soloing? The simplest definition I can give you is playing the notes of a chord while you're on that chord. Pretty simple in theory, but it does require some practice, and don't worry, it's well worth it.
As guitar players, we often play "over" the chords, meaning we're playing the proper scale for the progression, but we're not considering each chord as it goes by. Chord tone soloing is the opposite, as we're playing "on" the chord changes. We can treat each chord as its own thing requiring us to play or resolve to the specific notes of that chord. My first piece of advice is to learn as many chord voicings as you can, because as you'll see, that's what I'm thinking about first. It's important that you know the fingerboard and the notes of each chord, but that takes time. With this method, you can get started on chord tone soloing right away.
This course is in loose difficulty order, but the final tune is by far the most challenging. Have fun and please be patient with yourself, as this way of thinking requires some mental work, but it's worth every synapse you're creating!