Best ways to collect rent?

[Christie Broome]

We need to crack down on our tenants in the new year.  We have too many that pay late even when we've sent a pay or quit notice.  What wording do you use for tenants so they know you mean business?  Rent is due on the first of the month.  Our county allows a grace period, and late fees are applied the day that expires.  We send pay or quit notice as needed, but still have some that have abused that and we are filing eviction for.  What can we do better in the new year to collect rent on time?