VS2010:
In VB I can place the cursor inside an existing method's parameter brackets and type a 'space', which will bring up the tooltip with description of the parameter I'm at. This is not the case in C#. I have to delete the whole brackets including the parameters, and retype the left bracket, for this tooltip to show. Is there some shortcut or setting to change this behavior? I tried hitting ctrl, shift, alt, but it has no effect.
Ctrl+Shift+Space will do what you want.
You might want to check out a poster of key bindings.