You don't know what you are getting into until you are there. There are ways of getting information from outside sources, but the real truth of the cloud becomes apparent when you are inside of it. One thing we teach instrument pilots is what to do when you have inadvertently entered one of those clouds that you really wish you weren't in. For a pilot, this means to pay attention to just a few things. You slow to an airspeed that is safe for your airplane and loading. You keep your wings level as possible.
You allow your altitude and heading to vary in service of maintaining the key attributes that will keep you safe and your airplane intact. Most of all, you keep going. That is the technical part. There is another part that we talk about, and that is the reality that you are a human being sitting inside a very small piece of aluminum a mile or more above the ground with nothing in front of you but rain and clouds. In some cases you can't even see your wingtips. You might be alone, or you might have passengers whose lives depend upon you. That can be really scary.
In order to do the steps above, you first have to go back to your training and to your confidence in yourself . You find the place of calm that allows you to trust yourself, and trust the process of flying that has gotten you through all of your other flying experiences so far. That is probably the most important piece. Go to what you know, believe in yourself, stay calm, focus on a few key priorities, and fly yourself to the other side of the storm. Once you are in the clear, then you clean up your course and add in all of the other priorities. In the words of Winston Churchill, "when you're going through hell, keep going."