a quik ? about zooming

There are times (not always) when I want to zoom in using my mmb and the increments are too large, it zooms in too far too fast. I need to zoom in to say merge two verts that are real close together and when I start to zoom it zooms right past them. then there are times when I have no problem with it. Am I doing something that I dont know about? or not doing?

Select a point and use numpad . key to zoom into your selection or Shift+B and box select the area you want to zoom into or Ctrl+MMB drag to zoom

Thanks Richard,
But that didnt help much. I did notice though that if I put it in camera mode I get the zooming I want. (number pad or mouse). Out of the camera view though it still zooms way too fast and too far.

using shift-b seems to have fixed it. now even when not in camera view it zooms normally