Listen to what they say, even if you don't agree with them. In the beginning when your getting to know them, you have to stay neutral, voicing opinions can make a bad impression.
After a while when you all get more comfortable with each other and like each other more then you can be your true self. Ensure you have boundaries in your relationship where neither party surprises the other with unannounced visits. This can lead to annoyance.
Inlaws can be a great benefit to your life as they are like another family if you all get on well. But if you don't get on, then go shopping the day they are visiting.