Backup strategy. Part of my backup strategy is to backup to a USB twice a week.
Timing. Let's set it to every Tuesday and Thursday (since that is when it going to be busiest and therefore the chance of making a mistake and needing to restore from a backup is highest).
Snapshots. I keep at the most 4 snapshots of my documents folder. I try to keep the folder size as minimal as possible. At the moment my USB has about 28Gb usable space and my snapshots are around 100mb.
Manual process. At the moment this process is manual, but I hope to automate it soon.