Kudos to Microsoft for having an Implementation Methodology in their Microsoft CRM Installation and Configuration Guide. The book 8018A: CRM Installation and Configuration is almost three inches thick and in large 8 1/2 x 11 format. Just a bit of light reading ;~)
The point I really want to make in mentioning this is that you always want to create an Implementation and a CRM Roll Out Project plan or map. The Microsoft Project software can be used to help with the process, but even if you are not familiar or do not own MS Project you can use MS Excel to create a step by step, phased approach. Realize that installing the software is a very small part of the master plan.
Somethings to consider..
1) If you want to create custom fields and then who can do this? How will the fields change and grow? How will the data be controlled? Will the fields appear on reports? and if so which ones?
2) Who will be the small team of "first adopters"? Are their current processes documented or understood? Are they tolerant of change? Are they good at documenting? Will they report and then help track down any problems encountered? Are they decision makers who can pull the plug at the first little bump in the road?
3) Who and what are your support resources? and what kinds of support will you need? Software troubles? Infrastructure needs? Database Administration? Adoption? Customization? Can it do this type questions? How will the cost of such services impact your project, will you hesitate to use them?