• Use Action Verbs (not generic yes/no)
• Use Precise Diction (Remove vs. Delete)
• Use Task-Specific Language (Publish vs Submit)
• Use the Active Imperative Form (Read Details vs Click Here for Details)
• Use Sentence-Style Capitalization (Friendlier than Title Case)

Comment:
If you test people on an app the first time they use it, Title Case will slow you down, just as it probably did just now. However, it is much easier to see the shape of Title Case text in buttons than sentence case buttons.