How do I prioritize what to test?

Test prioritization balances potential impact against execution difficulty:

Impact assessment:

How much volume does this element affect? How large is the likely effect size? What is the business value of improvement?

Effort assessment:

How difficult is test setup? How long to reach significance? What resources are required?

Prioritization frameworks:

Start with high impact, low effort tests. Subject lines are easy to test and affect every email. Move to high impact, high effort tests once easy wins are captured. Avoid low impact tests unless resources are abundant.

Common high-value starting points:

Subject lines (easy, high impact). CTAs (moderate effort, direct revenue impact). Send time (easy, affects all engagement).

Not all tests are equal. Systematic prioritization focuses resources where they generate the most learning and improvement.