There are a lot of different CRM solutions on the market. We would never suggest to develop a CRM solution from scratch. Instead pick an existing solution and customize it for your needs.
The main choices for CRM solutions are:
At SSW we implemented a lot of CRM services based on Microsoft CRM. The experience with this solution showed us high trust in using Microsoft CRM as a base for future business needs.
Read the rules to better Microsoft CRM to get an idea what CRM can do for you.