When you are sizing up a consulting firm here are few suggested TO-DOs
___ Visit their office. Do you like what you see?
___ What is their head count? Does it seem like a good fit with your firm?
___ Ask how they are organized. Do you like what you hear?
___ What role does the 'mother ship' play if the firm is a branch office?
___ Ask, "What do you do about quality control?" If they have a QC team, that is a good sign.
___ Ask how much contingency you should include for change orders. More than 2% could be a problem. The M/E consultant's attitude to change orders is a good gage of how well their Quality Control works.
___ Do they carry professional liability insurance?
___ How will they schedule their work for you? Does it seem well-thought-out?
___ What is their procedure for estimating? Do they recommend a contingency to cover their accuracy?
___ Ask who you will work with. Assigning your project a project manager is a telling issue. If you will work with each discipline directly, my experience is that they don't communicate internally and you are expected to coordinate their work for them. Depending on your level of experience and available time, this can work; but good firms use a project manager.
When you find a firm that you are happy with and want to work with, the next step is to work out a fee and scope of work for the project under consideration. If the fee is higher than you would like, consider negotiating the scope of work they will provide to get the fee in line with your plans.