Things I know:
- The MacBook will be the computer
- I'll place an external display as well (19" probably)
- I want an external keyboard and mouse involved in ergonomic locations
- My phone cradle is a must
- I want to minimize plugins, so I'll have a USB hub cable, an ethernet cable, a power cable all in place.
I find it helpful to look at Mac desk setups for ideas. A printer-cartridge company pointed me to their recent photo gallery of Mac setups: 25 of the Best Home & Office Mac Setups.
A great way to get ideas is to scan some of the many Flickr photo pools.