If you’re like me, you like songs that can tell a story, even without words. In order to create a song that can tell a story, it must be able to communicate different emotions throughout the length of the song. This means that your song may contain several different themes all together. So, your song will need to be able to smoothly transition between the different elements. I find that the easiest way to accomplish this is to gradually (or suddenly) drop out most of the layers in your track, leaving only one or two different sounds or instruments. Then introduce a new element that sounds good with the last remaining layers, and use a buildup to introduce a new section. Now you can drop out those last remaining layers, and now you have a completely different vibe!
Another interesting trick is to find a nice long percussive sound and reverse it. Then, when you have the reversed clip in your sequencer, you align the climax of the reversed sound with the beginning of the next bar. This adds suspense, which is cool in my book.