Some points to consider if you are having some bespoke software written for you.
What am I buying?
How much will it cost me? How are the costs broken down?
Look at each of these areas in detail: work out the costs, VAT, consultancy, delivery, installation, integration, maintenance, support, upgrades.
Compare developers and ask them to tender for the same work based on the same specification.
What are the hardware/ software requirements?
Who will own the Intellectual Property Rights in the Software?
Are there any restrictions on use of the software?
Future proof in terms of your requirements.
Do you require the source code to the software? If the developer does not want to provide this will it be made available to you through escrow?