1.  Outside in the shade isn't good.

2. http://www.google.com/search?hl=en&q=how+to+photograph+art

How big do you want to print?  6x6 will do really good enlargements up to
around 24" square, more if they're to be viewed from a 'normal' viewing
distance, so unless you have big posters in mind, or need incredibly subtle
tonality, then 6x6 should be fine.

Copy lighting would be to place these two equidistant on either side of the
subject, at a 45 degree angle to its surface, aimed at the middle.  The
objective is for the falloff from each to mirror the other, so you get even
lighting from side to side.  With two lights, you'll need them reasonably
far back so that the falloff from top to bottom is minimised.  Use an
incident meter (or meter off a grey card) to take a series of readings  from
corner to corner to see that all four corners are getting the same amount of
light, and that they aren't more than half a stop - at most - different from
the amount of light falling on the centre.

(You might get away with a little more centre to edge difference than that
if you are usinmg print film, but even then I'd aim for no more than a
maximum difference of 2/3 of a stop.)

The 45 degree angle should also allow you to avoid any direct reflection of
the lights.  However, art work is seldom flat - oil or acrylic paints you
can see this is obvious, but even in pastel or watercolour the individual
grains of pigment can be at all angles, and can present reflecting faces to
the camera.  This can be hard to see, but results in an overall loss of
contrast and, particularly, colour saturation.  If it happens, the only real
answer is to put polarising filters on both light sources, aligned parallel
to each other, and another aligned at 90 degrees to them on the camera lens.

For a flat subject perspective isn't an issue, so you can be at whatever
distance from the subject you like - and so use whatever focal length you
like to suit that distance.  In practice the distance you need is often
determined by where you need to be to avoid reflections and how far back you
have an unobstructed view.  Subject to that, choose whichever lens you have
that performs best at that distance, looking for, in about this order: least
distortion; flattest field; sharpest (I'm assuming that good colour
rendition is a given.)

If the artwork is high in contrast, then maybe you would need something like
that - Portra 160NC rated at 125, say.  A better solution for very high
contrast subjects is duplicating film like Kodak E-Dupe or Fuji CDU II (both
of which I have used in 4x5 for copying paintings.)  For gentler contrast
ranges, however, I use a conventional slide film and would go for either
Fuji Provia or Astia.  Use an incident (or grey card) reading for the
exposure, but use spot readings to ensure that the subject brightness range
falls within the capabilities of the film you use.

For the digicam be sure to set a manual white balance.  You may need to give
as much exposure as you can  _without_  blowing the highlights, so that you
can tone things down later and preserve the shadow detail.  Colour accuracy
is not likely to be as good as slide film, and of course the resolution
won't match your 6x6 - but if nothing else this can be a good way to check
for reflections and evenness of illumination.

On an overcast day this can be a source of diffused light to use instead of
copy lighting, but it can give you problems with reduced contrast due to
reflections from the pigment grains.  Worse is that you may find the light
is too blue, and not easy to get accurate colour balance without some trial
and error.  This approach is OK for an artist to get quick records of work
in progress, but it isn't really a viable option for 'serious' records or
for reproduction.

That's about it.  Be sure of a sturdy tripod and make sure the film plane is
parallel to the plane of the subject.  It's worth taking extra care with
focusing too, using a magnifier if that is possible with your particular
camera.

Have fun,

Peter

What is the desired result, the end product?