Soundcloud allows you to share your tracks to groups, groups are a fantastic way of getting your tracks in front of users who like a specific genre. You can share a track to 75 different groups at any one time.
Groups are free and easy to create and there exist an almost unlimited amount of groups, so it is imperative that you share your tracks to groups that get traffic (there is no point sharing a track to a group with just 2 members!)
When you share a track to a group, it appears at the top of the group, this is when you are most likely to get users browsing the group to listen to your track. This is why it is important to make sure your track has an initial traction before sharing. A naked track here, is more than likely to be skipped over as not worth listening to. So do not share your track, if it is not ready to share, for more information on this, check out the blog post on giving your track a head start.