1. Articulate what you need the software to do.
2. Ensure these needs are aligned with your business goals.
3. Outline existing processes that the software will affect.
4. Note any problems or limitations.
5. Consider how these processes can be improved.
6. Determine and prioritize software requirements.
7. Decide whether to build or buy the software.
8. Identify all potential software solutions.
9. Match each solution with requirements and remove those that do not match.
10. Solicit recommendations from peers.
11. Narrow the list of solutions to a short list of alternatives.
12. Contact each vendor.
13. View product demonstrations with input from end users.
14. Speak with references.
15. Negotiate terms of contract.
16. Make final purchase decision.
Read the detailed article at http://www.capterra.com/docs/capterra-software-buying-guide.pdf