How to fit two surfaces exactly

i have two surfaces i need to minimize the deviation between them and match, how can i do that is there any method please help.

Impossible to say just from this short description.
Please post the Rhino file and try to describe the problem in a clear way.

Two surface which overlap, or two surfaces which need to meet at a common edge? As wim asked post a file and description of what you are trying to accomplish. Files can be posted using the vertical arrow on the tool bar above where you type your post.