Easy lick one: Keith Richards style rhythm
Here's a classic Rolling Stones style riff in Richards' favourite DGDGBD tuning. Make sure the pull-off s are clean and even whilst holding the chords down and use a confident strum to give this riff the attitude it needs. Try some classic Fender amp crunch for authenticity, using a bridge single coil.
Easy lick two: Muse style riff
A super riff in F# minor pentatonic (F#, A, B, C#, E, F#). Crank the gain and pay special attention to the hammer-ons, aiming to keep them smooth and as loud as the picked notes. The last 'A' note requires a bit of fretting hand fourth finger strength to bend the sixth string a little.