Im trying to ween my 18 month old from sucking a pacifier. how should i do this. can i give it to her when she goes to bed.

Techniques vary: You can do it as you suggest, giving it to her at only specific times, but I have found that parents who do that are too tempted to use it at other times, for instance, she bumps her head and is crying and you run and get the paci. If you really want to get rid of it , get rid of it. It just doesn't exist anymore.It will be a tough one week, but then the deed is done. It is much better in long run.