Best way to center caption and 'captionwidth' in Lyx floats

[viveksharma]

Hi
I have three questions:
1.This has been discussed before but can the lyx-latex gurus point me to 
the best way of centering tables, figures and their captions in floats
I remember having read that using the layout->paragraph->center command 
is not the appropriate way. I remember some discussion about having an 
appropriate vspace between the caption and figure/table.
2.I use Komabook and is their someway to define this in preamble and 
make the default table caption to be above and default figure caption 
below the figure.
3.Is there some way to regulate the width of the caption to be equal to 
the figure or table width?
Thanks
Vivek