Have 3-5 Objectives, each with 3-5 Key Results. Review & renew regularly.
Some tips for good OKRs:
Quantity
You should have 3-5 top-level Objectives. These are your main focus. These are what’s most important. If you’re focusing on >5 things, you’re focused on nothing.
Each of these 3-5 Objectives should have underneath it a set of 3-5 Key Results. These key results should be SMART, falsifiable goals.
Key Results Achieve Objectives
The Objective should be met by achieving all Key Results.
Also see: Good Metrics
Clarity
Key Results should have Red/Yellow/Green grading criteria.
Both the Objectives and Key Results should be written as though they were going to be read and interpreted by other people. This forces you to be specific and articulate.
Timing
OKRs are typically set and renewed quarterly, but there’s nothing saying it has to be that way. They should be a prime focus and reviewed bi-weekly at a minimum.