How Do You Handle a Lease or HOA Violation?
Discuss the issue with the tenant first. Most tenants only skim the leases in my experience and sometimes don't even know they are violating anything. And, hopefully, you are on good terms with your tenants so this isn't a big issue.
If that doesn't work, I suppose the next step is a formal letter advising them of the previous personal conversation and lack of subsequent compliance, with some kind of date for compliance. If that didn't work, I would give a final "X days to comply or quit" notice.
The biggest thing I see is people not keeping grass mowed or trimmed on edges. I have an addendum in my lease that offers lawn service for X dollars, and if tenants decline (I have them initial) they are required to maintain, and if more than one notice of non-compliance is received mowing services will be taken over by the landlord (I hire it out) and they will be billed as part of their rent.