Making Form Re-Sizable

AutoScroll

Set to true, to enable scroll bars when needed.
You can then just add controls outside of the forms size and the scroll bars will appear to allow then to be seen.

Minimum Size

Set the minimum size for the form

Padding

Set to force a bit of space after the last object on the form

Getting controls on a form to resize automatically when user changes for size

The flow layout panel is very useful

Dock

The Dock property of a control allows you to specify which borders of the control are bound to the container (which may be the form itself if the cotnrol is not inside some form of container).

Anchor

The Anchor property of a control defines the edges of the control that are bound to its container. E.g. set to bottom and right for a control to be glued to the bottom right corner of a form as its re-sized.