First rule: you are there to sweat - but not anywhere you like
Obviously, when you go to the gym, you want to work hard and be physically active. The benefits of this are well known, as are the consequences: sweating - more pleasant for you than for the people around you.
So, to make sure you don't leave a sweaty trail, wipe the benches, equipment and mats after you use them.
Out of courtesy, a nice smelling environment also requires you to wear clean clothes: wearing the same sports gear for several sessions may leave you smelling bad. It is not just in your head.
Here is some advice for cleaning your sportswear: