• Satisfaction of regulatory requirements
• Preservation of locally significant or valued cultural resources 
• PR value, i.e., being a good corporate neighbor
• Fast response, comprehensive documentation, and cost-efficiency
• Having someone on your planning team who understands how cultural resources impact you, as well as how you will impact them.  

What is the most important thing I should look for in choosing an archaeological expert?

• Reliability and experience
• Past performance on projects similar to yours
• Turnaround time (responsiveness)
• Overall cost

Any other advice?

• If you find yourself in a pickle because you didn't budget for the cultural resource studies that you're now required to do, it's coming off your bottom line.  So here's your early warning ... start lining up a cultural resource consultant early in your planning, along with your other environmental experts.
• It's always a good idea to hire someone who has a good working relationship with your state's State Historic Preservation Office and can satisfy their review requirements for a competitive price.
• To a non-tech person, all archaeologists "look" alike.  They all do the "same thing," have advanced degrees, and have field experience ...right?  Maybe.  Rather than hiring the first archaeologist who gives you a low bid, make sure he/she has considered all contingencies and aspects of your project AND has a good working relationship with your reviewing agency(ies).  Talk to other people in your field who have used archaeologists, and find out who they recommend and why... and who they don't recommend and why.  Talk at length with potential consultants.  How aware are they with what you are facing in your particular situation?  How responsively do they treat your concerns?  After all, this person is going to be a member of your team, giving you advice and recommendations.  How easy do you find him/her to communicate with?  If you click with your consultant right off the bat, you will usually have a rewarding relationship.
• There is really no subsitute for choosing a consultant by working with him/her and deciding on that basis.
• Don't forget the benefits of doing archaeology from a sales and marketing standpoint.  Insofar as heritage value is concerned, many developers believe that it's just the right right thing to do.  "Some lands simply shouldn't be developed," is how one of our clients put it.  Others can be showcased by reference to their historical landscapes.
• If need be, be prepared to choose another property to develop if the one you first considered is just too "hot" from a cultural resource perspective.  The time, headaches, reputation, and $$$ you save just might be worth it.