To become a fantastic daughter-in-law, you should be ready to treat your spouse's parents the same way you'll treat your parents. A woman should understand that once she entered into a marriage with her husband, everything about her husband becomes her priorities.
You didn't get married to him alone but to his parents and relatives. You shouldn't start your marriage life by thinking all mothers-in-law are wicked. The fact is there are wicked ones, and there are good ones. In fact, human beings are generally evils, and this trait can show up at any time. Be a good daughter-in-law to your spouse's parents.
Seek their advice as though they were your real parents. Don't get used to the mentality that your mother-in-law does not like your relationship with her son. Visit her regularly and help her with some things. In short, be nice to your spouse's parents and relatives, and they'll also do the same to you.
It is sometimes tough for people to become good daughters-in-law because they know that their in-laws may not like them that much. There are some in-laws that you cannot please no matter what you do, but there are also some that will defend you even from their sons.
The best thing that you can do is always to become pleasant. Make an effort to listen to what they say, and you have to make sure that you will respect them. When they see that you are making an effort to get to know them better, the more that they will love you. Your effort will surely make a lot of difference.