What I did was create the base of my cabinet first.
Basically it amounted to a rolling table that held the computer inside, and the CP/Monitor on top.
That gave me something to tack cardboard mockups of the side panels, monitor bezel and marquee area to.
I just cut the cardboard, stapled the sides to the table thingy, and then taped the pieces in to make the marquee/monitor bezel.
Once I got them exactly the way I wanted them, I measured them, marked up the plywood, and cut it.
My general goal was to have a cabinet similar to an Asteroids/Star Trek machine.
(Near Vertical monitor, with cabinet sides swept forward slightly).
I wanted the marquee larger than the original, so I made that the size I wanted and worked to match the cabinet to it.
I highly recommend this method if you aren't SURE what you want at this point.
It is alot easier (and cheaper) to throw away some cardboard, and start over, than to get the cab half done and realize it's not what you want, or won't fit the hardware you've got.