1. Add data to ArcView project.
2. Click on "View" menu and then on "Properties...".
3. The Properties window will come up. Click on "Projection..."
4. The Projection window will come up. Click on the "Custom" radio
button and then find and select "Lambert Equal-Area Azimuthal" on
the "Projection" drop box. Finally change the "Central Meridian"
value to "-100" and the "Reference Latitude" value to "45". Click
"OK" when done.
This example is for setting Lambert Azimuthal Equal-Area projection
for the contiguous United States. If you are using a
different projection, change the "Projection" drop box
appropriately. You will also have to change the Projection
parameters.
5. You will now go back to the Properties window. Change the
"Distance Units" to meters and click OK.
6. Your View should now look like the one below.
7. Feel free to recenter your map. Click on the View menu again
when you're satisfied.
8. On the Properties windows, click on "Area of Interest..."
9. The Area of Interest window will come up.
10. Change "Set AOI to" drop box to "View". The extent will be
displayed. Copy this extent to your map file.
If you're clueless as to how you'd use the extent (AOI) in MapServer, here's a clue: EXTENT X1 Y1 X2 Y2
If you still don't know...
EXTENT 199949.651166 -371954.772084 1472121.6862 632767.19157