The trouble is that, in my experience, there is very little discussion that goes into the dangers of various forms of augery. Those that do are typically looked at from an uber-religious "thar-be-demons!" perspective which is altogether unhelpful. My intention here, is to throw a few ideas out there to get folks thinking on this subject.
Before the alarmists get started in, I should note that I have yet to see someone be possessed on account of sortilege. I've ne'er had to exorcise an unwitting victim on account of them having thrown some bones whilst attempting to discern the future.
I have, however, been forced to involve myself when folks have screwed things up for themselves by acting on incorrect information and, worse yet, have dealt with situations requiring remediation on account of persons becoming too emotional on account of what they've seen. Some individuals aren't aware of just how their strong feelings influence the world around them, and these are the problem children when it comes to divination.
They are troublesome because they have the ability to do magical things, but cannot control themselves. Instead, they unconsciously react to knee-jerk inspirations and cause situations to worsen or become nigh untenable. They either take the information to heart and start acting out in the physical realm, or they become so damned fixated upon the negative aspects of a situation that they reach out, metaphysically, and wonkily turn the Dharma Wheel, so to speak. In doing so, workings can be jilted off-course and the scene can spin out of control.
We often perceive what we want to see or otherwise feel the need to see, and this can be great....it can also be really negative, as we create our realities with our self-chatter. That internal push to be [x], do [y]. or react to [z] can either help us or get us into a great deal of trouble.
We revert to what we're comfortable with as a point of fact, yet give relatively little thought to how that affects us or the situations around us. This is strangely pertinent in divination for two reasons:
1) We will usually see what we want to see.
2) We often take action on what we want to see, and that's not always good or valid information.
Dealing with #1 is relatively easy, and #2 depends on how we deal with the former. When getting started with divinatory work, I recommend being highly suspicious of anything that confirms your thoughts on the matter at hand; I would recommend going as far as to have your readings checked by someone you trust until you get the hang of your mind's inner workings and feel that you can accurately use cleromancy to your benefit.
It helps to stay entirely neutral and to go into the reading with purpose, but without agenda. If your intention is to learn of the best way to handle a situation in a way that is beneficial to you and you've suspended pointed desire, you're generally able to get true information that's worth reacting on. This then renders both sticking points, mentioned above, as relatively moot.
#2 is harder to deal with because we are very good at deceiving ourselves. Worse yet, when we get something that confirms our bias, it excites/saddens/elevates/deflates us, and so being resolved to read the truth is necessary.
The advice I use, in short, is to stay neutral and view Tarot as entertainment TV until the result is in. Augery should be treated with respect, and so too should those who provide such a service. Keep an open mind with your readings, as the information can surprise you from time to time. That has to be ok, as its better to get correct information that bothers you than it is to get wrong information that causes problems.