Getting into lead guitar and melody writing can be intimidating at first, there are so many scales and techniques available that the beginner player can feel quite intimidated. But things can be made easier if you cake a chordal approach to your lead. In other words, instead of playing in a scale to come up with a lead part, we'll simply play notes from the chords you are playing over. That will always work and always sound very good. 

Let's take a look at the chord progression we'll be playing over:

A - G   - F#m - E
D - C#m - Bm  - E
A

Let's now try to come up with a melodic theme making sure stick to the chord you're phrasing over. Once you are comfortable with that exercise, you can experiment with additional notes within reach of the chord you are working with. Your ear should guide you in the choice of possible embellishments. This can work with any chord progression, no matter how complex the chords are and is always a great way to come up with themes you can remember.