Arrange lots of playdates with other kids.
That would depend on why i did not like them. Kids are going to do whatever they think they should and if you were to forbid them from seeing these friends they would probley do it anyway.
I would encourage that child to chose their friends carefully
First, depending on their age (mine are all grown), there was an on-going discussion of values and being confident enough in who you are to not be easily influenced by peers who don't share your values. That can't be a reaction to a "new" friend that I don't like, it has to be part of their growth process. Second, I spent a lot of time getting to know their friends. I suspect it is difficult to "not like" a child that you invest some time listening to and understanding. Finally, if after all that, the "friend" was disrespectful to either myself or my child's values, I found that my kids were simply not interested and I didn't really have to do anything specific. It worked well for me, but maybe it wouldn't in every situation.
It all boils down to doing the right things in life. With this in mind I would teach them so. Children are children. We did not do the right things all the time did we? We had our own friends some seemed bad in the sight of our parents but they we good in the end. But we will need to explain why our kids should keep away form the "bad" ones. One the kids know the reasons then, we will find it easier to convince them.
You can only teach your kids right from wrong after that its up to them.if you go to picking their friend,they will only hate you for it.As was the case with me only time taught me, mom was right.that my friends where fair weather friends.its kind of a two edage sword you dam if you do and dam if you don't.
It depends on why I didnt like them. If I thought they were a bad influence I would probably move. keep them apart. Part of our job is to keep you innocent as long as possible. If my parent gave two ***** about me they would have kept me away from the crowd I hung out with in HS.