Three C's: Consideration,company and cleaning. If you get on with your flatmates then that is a huge bonus. Hogging the bathroom at 0830am on a weekday is an activity that will corrode your flatshare in three days flat. Try cleaning things (like your plates and cups) and vacuuming the living room occasionally. Don't suddenly bring strangers into the property to stay without warning. This is really disrespectful of other peoples' home.
Consideration is about thinking is my music too loud, did I slam the front door on the way in at 2am last night. Has my girlfreind been here too long. Is it my turn to feed the cat. Am I talking too much or too little to my flatmates.
Company is about not staying at the flat or house all day everyday: give other flatmates time to be alone at home too. Company is about saying hello when you come in if people are in the common parts such as living room. Company is about not staying in your room all the time.
Cleaning is about accepting that dirt drives some people nuts. Cleaning is about not leaving hair in the bathroom sink. About switching the dishwasher on, not just putting things in it. Cleaning is about looking in the toilet after you've used it to make sure you didn't leave too much evidence of your use. Cleaning is about finding something as you might wish to find it yourself.