Build up speed - Metronome
Following that, start building up speed. We suggest grabbing a metronome and if the riff is 120BPM - Drop it right down to 60/70BPM and work up in 5BPM measures until you’re playing at speed, you’ll find that you reach a few hurdles, but all of a sudden, the riff will ‘click’ and you’ll be surprised by how fast you’re playing! The metronome also helps you build that ‘internal metronome’.
Hand strength & Warmups
Ever played a riff and just felt that your fingers can’t get there fast enough? Wrist ache when playing a barre chord? You might need to work on your hand strength. There’s a bunch of hand exercises online as well as adjustable hand exerciser tools that you can use to improve strength and dexterity. Also it’s important to remember you shouldn’t jump into playing a riff cold, run some playing exercises before attempting that solo. Another useful tip is to try to avoid playing guitar with cold hands, you’ll find that you struggle to move your fingers as fast!