They sit on the other side of your desk and answer your questions levelly and with appropriate detail. They seem affable and well informed, and in the end you write up a contract. They join your team, ostensibly for the duration of whatever monster project is looming. You give them several sizeable checks. Some might leave while you still need them. But even if a consultant stays for the duration of a project, you may not have hit that critical milestone that you thought their expertise would ensure.

Selecting the right consultant can frustrate even the seasoned development manager. But, if you ask the right questions and can read between the lines of their answers, you can usually choose one that proves to be a good fit. Below, I’ve compiled a series of five probing questions that you should ask consultant candidates. I’ve also included descriptions of acceptable and unacceptable answers and tips on how to decipher their responses to help you make the best choice of candidates for your development needs.

What, specifically, was your approach to the last project like ours that you completed? And what about the one before that?
The key part of this two-part question is the phrase “and the one before that.” When you ask a potential consultant to reveal his or her approach to problem solving by citing a specific example from a prior job, you’re likely to get a perfectly satisfactory answer.

But with only one response, you really haven’t gotten much useful information. When you ask about at least two previous jobs, you can compare the details. If the consultant’s effort on Implementation B was more or less the same as Implementation A, you may have in front of you a fairly uncreative, by-the-numbers worker. If, on the other hand, you hear a second story as rich with detail as the first, but with differences that indicate attention to the uniqueness of the second implementation’s environment, you’ve probably found a consultant who will diligently tailor the project to your specific needs, and not just do a repeat of a previous job.

The rate we’re offering you is the top rate for your specialty and other not-so-rare specialties. Is it satisfactory?
The phrase, “other not-so-rare specialties” is the prima donna filter. The reason you’re shelling out big bucks for a consultant in the first place is because that individual possesses skills not found in-house. You’re in a negotiation phase right now because of the rarity of those skills, but the skills alone won’t get your job done. Those skills need to come in the form of an individual who will work well with your in-house people.

If the consultant takes this information and attempts to parlay the rarity of their skills into a higher rate as a matter of status (which is what this question is designed to determine), you have a consultant with a view of self that is built primarily around the skills—surely not the best solution. When this question triggers additional negotiation—however subtle—you’ve been given an equally subtle sign that this isn’t the consultant you really want.

Look for the consultant who dismisses the question with an easy affirmative. That’s the team player, the professional whose self-perception is based more on character than talent.

According to your resume, you served in this capacity and were responsible for x. How did the projects turn out?
The jobs you want to hear about are the short ones—the 90-day wonders. Those are the ones you should cite in your question.

What you really want to know about those jobs is whether the consultant was around for the end of the project. Does this consultant have a knack for finding really short projects, or does he or she just get bored and move on? It’s commonplace in the consultant’s world to chase the next check, not the completion of the project. Since you generally contract such individuals for some fixed term with possible extensions, you can expect that some will jump ship at the end of the initial term for an extra $10 an hour elsewhere, no matter if the job is done or not.

The wrong answer to this question would be a vague one or an open admission that they weren’t around at the project’s end. However, you should determine whether this occurred once or a number of times, as subtly as you can, by asking about other complete projects. The right answer to such a question would be a credible story of a project completed, regardless of whether it was a short project or a long one.

May we agree upfront on terms for an extension of your contract?
Of course you may want to build in some reasonable incentive for a consultant to remain, particularly if the consultant’s home base is in another city or state. But you can spot a potential problem if the consultant will not agree to the particular terms up front.

As the project planner, you try to make a good guess at how long you’re going to need to pay out the high rate for this consultant, but you know you’re going to miss a bit on one side or the other. You could end up needing the help another six weeks or more, and if so, you’ll want to entice them to remain until the job’s done. You don’t mind building in an incentive.

But a sly consultant will take advantage of you here, and drive the rate up unreasonably because you’re over a barrel. How do they do this? By never bringing it up in the initial interview.

When you bring it up, there are two possible answers. The one that flashes red is, “Oh, we can talk about that when the time comes.” The answer you want to hear is, “Certainly.”

Have your past projects required overtime? If so, how much?
Identify a particularly difficult assignment listed on the consultant’s resume, especially one that demanded overtime. Ask if it required overtime and add a follow up question about how much.

If you can identify a project from the consultant’s resume that was both difficult and achieved in a tight time frame, the only reasonable answer is, “Yes, quite a bit.” If you didn’t find a project like that on his or her resume, fish for such a story during the interview, as innocuously as possible.

There’s a personality type out there in the consultant’s universe that is compelled to try to convince you that everything comes easily to them. This consultant will answer your loaded overtime question with a casual, “Oh, not much.” This tells you one of two things: this consultant is going to try to color the realities with some spin control—which you don’t want—or this consultant just doesn’t do overtime. Both types are bad news. You’re paying big bucks here, so you want someone who will see you through crunch times, which can translate into long hours.