Check out this video by Arvid Schneider to pick up a few things about working and rendering in Arnold.
Arvid Schneider shared a video on his YouTube channel called "My Top 12 Valuable Tips While Working and Rendering with Arnold | Tips, and Tricks". In this video, Arvid shares his tips that he learned during working as a VFX artist. Arvid notes, that the tips are applicable to other DCC and are transferable to other engines like Renderman or V-ray.
You might know Arvid from Arnold Intermediate Courses, a series of tutorials by Arvid on working in Arnold. If you haven't seen it yet, I strongly suggest doing so by clicking this link.