There are lots of great web development firms to choose from and with a little work you can probably find one who is a perfect fit for your needs. Ask these questions up front and make sure you are comfortable with the answers before you sign a contract.

1. How Long Have You Been in Business?

While you may not want to write off a great company just because they are new, you should certainly know about it before you enter into an important relationship. Running a web development business is difficult and often the margins are thin. If it's important to your project that the company you choose is going to be around for the long haul (rather than a simple cash and carry project) then certainly the longevity and experience of the firm becomes much more important.

2. How Many Projects Have You Completed?

In most industries there is no substitute for experience and web development is no different. When a web design company quotes you a price it's not like bidding on the construction of a building where a thorough blueprint already exists. Especially when any custom software is involved there are often a lot of unknowns that a company must build into their quote. The more experience a company has the more confident you can be you’ll get a great product when everything is said and done.

3. Who Owns My Site When it's Finished?

When you see it in print this question might seem obvious but it's often overlooked in the interview process. Be sure you get the answer you want for this question and it is adequately spelled out in the development contract. Also, when you finish the site make sure you get an archive copy for your records.

4. Do You Design in CSS or Tables?

There is a big difference between designs put together with well-formed CSS and table-based design. While they both might look the same, the latter is an out-dated way of building sites and if you’re going to build a new site you might as well have it put together correctly. Plus, CSS designs generally work better for search engines because the content is more accessible and the presentation code is more succinct.

5. What Is The Design Process?

This isn’t so much a differentiation question between multiple competing firms as it is a question that you should probably know the answer to. Knowing the answer will help you make better plans and organize your resources appropriately to complete the project. Additionally you should make sure that the process is appropriate to what you think will be necessary given the nature of the project. Things such as the number of design revisions allowed may be important to you.

6. What Happens When The Site Is Finished?

If you feel a long-term partnership is important to your success you should find out what happens when the project is completed. Some companies are pretty good at an initial project but are terrible at support and maintenance. Get a good understanding of how your account will be managed after the project is completed and what kind of resources you can count on for the remainder of your relationship.