I suggest you do that as well, because it really makes a difference. We looked up some maps that showed which rivers are gold-rich. Here in Sweden there are two types of rivers: one coming from the forest and the other coming from mountains. Gold prospecting you should only do in a river coming from the mountains.
Most gold you will find on the bedrock, and black sand is a good sign as well. In the river where we were, you didn't have to dig deep to get there at all, which was nice.
Definitely a cool experience and if you want to find gold yourself, do it for that, not for money. With just panning, it takes quite some time untill you can actually earn something with prospecting. Sweden is a good place for gold, but don't expect any nuggets!