So, here's how you should take action if your in-laws hate you (or you just don't feel that close to them or there is lingering bad blood from arguments about the wedding or whatever else):
Step One - Talk to your spouse.
Tell your husband or wife how you are feeling about his or her family. Explain why you feel this way. Be sure to use the tips for improving communication and avoiding communication mistakes featured on the site. Stay calm. Be careful not to offend your spouse's family. Instead of saying, "Your mother is a witch, who criticizes everything I do because she thinks she knows everything," say, "I feel as though your mom is disappointed in me. Some of the things she says to me make me feel as though she thinks I'm inadequate." When you're venting to yourself in the mirror after you've spent the afternoon with your mother-in-law, feel free to call her all the names in the book. Just don't share this with your spouse. It just causes hurt feelings, and it will do nothing to solve the problem. In fact, it might just start a fight with your spouse.
See if your spouse has advice for you. In an ideal situation, your spouse will speak up on your behalf. He or she has the inside connection with the in-laws and can probably better communicate whatever it is you are feeling. Since your spouse has been dealing with the family of origin for a lifetime, he or she can better navigate the situation. Sooner or later, you'll have to get in on the conversation, but this is probably the best way to begin - let him or her pave the path for you.
Step Two - Apologize, forgive, and forget.
Now's your chance to be the bigger person. The conversation about changing the relationship or getting over past fights has been initiated. Rather than exploding and spewing all the venom that has been building inside of you, simply apologize for whatever role you played in creating this tension. (Even if you think you didn't do anything wrong, your in-laws probably feel as though you have, so that should be enough to warrant an apology.) Then, forgive them. This one is a little harder to do than it is to write or say. It might not happen overnight. But slowly try to replace the hurtful memories with good ones. And try to focus on the positives, especially if they are working with you to improve the relationship. Whatever you can forget - that blasted slight at your husband's cousins baptism or the failure to help pay for the wedding, leaving you and your parents to foot the bill entirely - try to put out of your mind. The more you hang onto these feelings, the more you stew, and the sicker you become. It will work on your nerves, stress you out, and put you in a bad place with your spouse. And because hate begets hate, you are just creating a never-ending cycle.
Step Three - Try to meet their needs.
In-laws, much like spouses, are not mind readers. You can't possibly know what it is your in-laws expect from you. If you haven't talked about what they would like from you (maybe it's dinner once a month and some alone time with their son, your husband), you'll never know. Once you've cleared the air and decided you're going to work on this relationship, ask your in-laws if there's something you can do to improve things. Ask straight out what they expect of you as a daughter-in-law or son-in-law moving forward. See if it's something to which you can agree. If it is, great. If it isn't, try to explain in a diplomatic way. For example, if they want you to change your last name to your husband's and you don't want to do that, you can say something such as, "We have decided that I'm going to keep my maiden name because I have had it all my life, and I established my career with it."
Of course, the road goes two ways, so they should ask the same question in return, and you should be prepared to answer. Perhaps, you would like them to call ahead when visiting, rather than dropping by like they do now, for instance. Speak up now about whatever it is you need to make the relationship function better for you - or forever hold your peace.