The best sign of a good pitch is its cleanliness. If you are considering whether the pitch you have just discovered is suitable for wild camping, look at the ground. A lot of cigarette butts, empty bottles, or shards can be an indication that the place is visited by other people, and you are not as alone, as you might think.
Wild camping rules in Sweden: "allemansrätten". There are general "allemansrätten' in Sweden, which translates to the rules of public access. Basically, you are allowed to roam all of nature, to pick any wild berry or mushroom, swim in any lake, access any beach, and yes, pitch your tent in any public area.