You don't have to take a class. You don't need special training. You do not necessarily need a guide.
But you have to be willing to give him everything.
Yes, I mean it. All. Everything. The totality of your life, your loves, your likes (your dislikes), your stuff, your concerns, your you. ALL. But you also have to be honest. That is why knowing yourself is so very important. If you want to know God's will; I mean, if you really only want to know what he wants so you can do it, it won't be all that hard. But if you want to know "kinda" or "as long as he doesn't ask..." then you will be chasing yourself in circles.
The first step is to find any blocks. Dealing with them may take a bit, but you can't deal with them if you don't know they are there. You don't need to be afraid that God will "get you" for them. It's not like he doesn't know they are there, after all. Start the process in reality. What are you willing to give? What aren't you willing to give?
And always, why?