If you feel the need to have a "psychic" present or if one has been strongly requested, and your comfortable with it keep as MUCH information away from them as possible and try to get their TRUE readings.
Watch for the psychic fishing TOO much. It's cool for them to ask, "Is this a spot where things have happened?" but if they then ask "And what has happened here?" I hate to say it but, it's a good possibility that their "reading" will mirror the reports or what the person said in a large degree.
Now, I will not suppose that ALL psychics are frauds, some people do seem to have a special gift and some that don't still mean very well.
Just make sure you take it all with an open mind and follow your own instincts. What if your psychic told you in the one of the larger Canadian forts to concentrate your efforts on building #5, the powder room, and you sent your best equipment and team there for the whole investigation; only to find out that the small contingent you sent to Barracks B ran into more than it's fair share of phenomena and had few people to document it and almost no equipment.
Please do use people to the best of their ability, but use your own good judgment too.
In the past we have had many people dying to use "Angel Boards" or "Ouija Boards" while out and about on investigations. NOT GOOD! Aside from the fact that these items are the EASIEST of all things to manipulate, even psychics tend to shy away from their use. Take whatever stand you want, here's BOTH arguments against them...
#1: Ouija's are a dangerous and uncontrollable device that can unleash ANYTHING from the "spirit world" into our realm. Once there, this new entity may control events to such a degree as to screw up any "real" investigation.
#2: Ouija's are a dangerous and thoroughly controllable game mass marketed by Parker Bros. that can either induce your team to conjure up nastiness from their own subconscious that will affect their usefulness on the investigation OR some twit will lead the overzealous to believe something as a joke that isn't true and that will also affect the outcome of your investigation.