How do I handle employment gaps?

I have a [length] employment gap from [dates] due to [reason: layoff, family care, 
health, education, travel, etc.]. Help me:
1.
Decide whether to address it in my resume or save for cover letter
2.
Frame any relevant activities during this time (freelance, volunteer, courses)
3.
Create bullet points for productive gap activities
4.
Suggest how to format dates to minimize focus on the gap