Also make sure to hire someone who has done it before if you want to go that route. "Racking" is an art-form in itself and the cabling alone can turn into a real problem[1] down the road if you take it too lightly for too long. You also want to plan for redundancy, power density etc. from the start.

Sorting out messy cabling or adding redundancy to a badly managed rack on live hardware is not fun.

[1] http://www.vibrant.com/cable-messes.php (for reference, this is what it should look like: http://royal.pingdom.com/2008/01/24/when-data-center-cabling...)