My question is how to shorten the chair legs properly so they
sit and look good.

I do this to all my chairs (as they slant like windsor chairs, so
putting the felt bottoms on for hardwood floors wears the felt out
prematurely).

I put a piece of 1/2" mdf (or anything else more or less flat) on top
of my tablesaw (which is very flat). I then place the chair on top. I
use my combination square to scribe the bottoms of the chairs. It's a
two piece design (like this:
http://www.leevalley.com/wood/page.a...91&cat=1,42936). The
main square part I put all the way to the bottom (like the picture
where the device is used to measure the height of a blade). The bottom
part should be easy to slide around on the mdf (or whatever). Then use
the combination part (the smaller part on top) and switch the edge of
the measuring piece from rounded and smooth to the blade side (a small
phillips is all that attaches it, you can kind of see it in the left
picture on the link above). Once you have the blade (or scribe) set
then you're ready to go.

With the bottom part locked so the sqaure slides freely around on the
mdf then you hold the chair in a way that it doesn't wobble (sometimes
one leg is slightly shorter than the other three -- hold it down on the
other three). Now align the scribe to the highest part of all of the
legs (if you have one in the air it's that one). If the legs are
turned they'll probably be highest on the outside edge. Once you've
figured the height, lock it in with the set screw on the
combination/scribe part of your square. Now all you have to do is
slide the scribe around each leg (holding the chair just like before --
although I tend to move the chair so each leg I scribe is in front of
me, not a science, just whatever works). The line that is scribed is
your cutting mark. I have a thin kerf Japenese style flush cut saw
that I use for cutting the bottoms off of each chair. If the cut line
is hard for you to see you can make it more visible by rubbing a pencil
or even an ink pen in the line created by the scribe.

Something else I've learned that will be helpful is that when I cut
each leg I put the chair (or stool) down on a lower table (I have an
assembly table that is a nice height) and I put a towel under the seat
(hardwood seats) and then I clamp the seat to the table (make sure the
back of a chair doesn't rub against the edge of the table). Now I
simply eyeball the cut and hold the blade of the saw against my
thumbnail and slowly start a cut. Once I get going a bit I just go at
it and as long as I start right it will cut correctly along the line.
When I get to the end of a cut, to avoid splitting off the the last
part of the wood I will hold the top piece of waste wood down with
slight pressure against the saw and then I slowly finish the cut (a
sharp saw is best obviously).

Good luck, do a barstool first if you're nervous and once you get the
hang of it it's a piece of cake.

Mike