Questions to ask internally before you talk to a Vendor:
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1.  What are our primary objectives for a tool?
2.  Describe the organizations development and testing process / methodology.
3. What type(s) of testing are we doing currently?
4.  What tools do we currently own / maintain?  (Purchased and Homegrown)
5.  What language(s) is our application developed in?
6.  Is the application web or browser based?  If so, which browsers and versions do we test on.
7.  What operating systems do we test on?
8.  Are there any third party controls or grids?
9.  Are there any Active X controls?
10.  Do we need to test server side com objects or other parts of our application not accessed by a GUI?
11.  Describe the application architecture?
12.  What is the communication protocol between the different tiers of the application?
13.  What databases does our application work with?
14.  How do we create our test data?
15.  Are we trying to validate data in the GUI or the back end database or both?
16.  How often does our group test new builds of applications? 
17.  Do we have a dedicated Test Lab or would testers be using their own desktops?
18.  What amount of money are we budgeting for this project / tool?