Discuss the issue with your spouse. If anyone knows your in-laws, it’s your spouse. You should try to find out what they do and do not like in people so you know how to act around them. You may find out that your in-laws do not like when someone is “too nice”, so to speak.
Treat them with respect. Unless they’ve done something terrible (such as abused your spouse or something of that nature), you should treat them with respect. Respect goes a long way, and you might find them being able to open themselves up easier to you.
Act polite. If you put up an attitude, they’re less likely to take to you. However, if you say your please and thank-you’s, they will most likely see you as a friendly, approachable person.
Smile and act as though you’re glad to see them. This will most likely cheer them up about seeing you, as well as making you appear friendly.
Bring gifts that interest your in-laws. Gifts are a great way to show how much you like someone. Find out what kinds of things your in-laws are into, and give them presents. Make sure you remember birthdays!
Talk to your in-laws. You can talk about an array of things. Discuss what you both have in common- it will lighten the atmosphere, and you may be surprised to find how many similar likes you both have. Try to avoid arguments, as that can quickly turn into bitterness against you.
Become comfortable around them. If you act tense and uncomfortable around them, they may become the same way. Your in-laws may become offended if you act distanced from them, and may think that you do not like them.