Include 4 ads per campaign
Including 4 ads will help you reach more people with your campaign! For example, you could create four separate Company Page posts and sponsor them in the same campaign. Or, you could create a brand new ad in Campaign Manager and test four different variants of your copy and image in a single campaign -- all without posting all these different variants to your Company Page with Direct Sponsored Content. Learn more about Direct Sponsored Content here.

Test more than one creative within the same campaign to identify top performers
Make sure to set your campaign settings to “rotate variations evenly” as the system defaults to “optimize click through rate”. Once you’ve identified your top performers, switch it back to “Optimize click through rate” so your winning creatives deliver impressions.

Add unique tracking parameters to your URLs
This will enable you to get a clean read on post-click performance.  Run all A/B tests for a minimum of 2 weeks and only change one variable at a time.

Monitor specific metrics when optimizing your creative
For example, when refining ad copy, focus on CTR (click-through rate). For leads, make lead submissions your primary goal.
Allocate a sufficient amount of your campaign budget to testing: a good rule of thumb is 20-25% of your total budget.