How do I deal with Rapid Growth?

Hello everyone! I am an IT manager at a small (60 employee) company. My company recently has started to grow very rapidly (nearly 4 a month). By the end of the year we are looking at doubling our capacity and tripling the amount of data we work on.

Of course we are going to have to purchase servers, workstations, networking…etc. What I want to know is where do I start? What problems do I need to identify before I even start planning? What resources can I use to help me?

Any help is greatly appreciated!