Avoid anything that draws too much attention on itself when you’re scoring dialogue. This applies especially for instrumental solos but also for uncommon playing techniques or strange registers. Dialogue score usually needs to be as un-obtrusive as possible or it will quickly feel like overscoring.
Also take care to not write rhythmically too densely. Every rhythmical attack in a cue draws attention on itself so having a chord change every second is also not the most ideal choice. Dialogue scenes are usually not the scenes to show off your skills so try giving them the right tone with simple yet effective compositions.