My tenant always either pays late or never pays at all. He has not paid the rent for 2-3 months now. What can I do about this? :confused:

If you are in the US then you will have to start by sending a written notice giving the tenant a certain amount of time to either pay or vacate the premises. If the tenant fails to do either then you can file a lawsuit for eviction. Go to http://realestate.findlaw.com/tenant to read about evictions in general and then click on the Resources link to get the specific details and notice requirements for your state.

Have him evicted.

You are going to have to follow certain laws and procedures. That is, give him 30 or so days notice, etc.

The law is different depending on where you live. It varies from province to province, state to state, country to country.

What nation or country, if in the US,
First what does the lease or rental agreement that you had them sign before say?

Odds are if you are not doing anything after two months you did not do a written agreement either.

There should first be a written lease saying how much the late fee is for late payment. At this point, you will have to give them a written notice to move out ( depending on state you have to give a 15 to 30 day notice.
If they still don't move out, you go to court and file for eviction. There will be a hearing, and then they will be evicted by the sheriff office