This may seem like a no-brainer, but you'll be surprised by how many people don't bother closing the door all the way when they use the restroom.
Check under the door, and if you see feet, go to another stall or wait for the person to finish.
Don't confuse the restroom with a conference room. It's not the place to chat about business or hold long personal discussions.
Be respectful of the personal space of others and never look at another man as he does his business.
Don't chat on your cell phone while using the restroom. That's just rude.
Before you leave the restroom, make sure you flush the toilet. You don't need to leave something behind for the next person to deal with.
If you use the last of the toilet paper, soap, or paper towels, show respect for the next person and replace it. You can inform someone about this needs.
Never leave a restroom without washing your hands. Dry your hands after washing them.
Ladies, do what you need to do and then get out of the way as quickly as possible. If there is a restroom attendant, thank the person and leave a tip to show your appreciation.
Whether you caused the clog or someone before you did, make sure the host or office manager knows about it.