Typically there are a couple of small "buttons"
underneath the bottom slat of the blinds. These
have a hole in the center; a cord feeds down through
the blinds and is knotted on the underside of the
button. When you pull the cord to raise the blinds,
the knot causes the blinds to go up instead of just
having the cord slip back through the holes.

Anyway, pop the buttons off with a screwdiver and
untie/clip the knots at the bottom of the cord. You
will then be free to remove as many slats as needed.
Remember - you need to put the original bottom slat
back at the bottom. Cut the little "ladder" like
strings that helped hold the slats, reinsert the
buttons, rethread the cords and retie the cord knots
just below the buttons. Remove any remaining cord
below the knot.

Ron wrote:

I have bought some blinds from home depot that are too long. How do I
remove the extra pieces of wood to make them shorter so there isnt so
much at the bottom when lowered?