First remember that there is no right or wrong way to sequence, arrange, compose or write music. There are certainly popular methods which you can hear in most pop songs, and these techniques are woven into rock, country, blues, folk, punk and many other styles. It's often harder to hear that format in classical works. Contemporary pop music usually follows a pattern similar to intro, verse, prechorus or bridge, chorus, verse prechorus, or bridge, chorus, break, prechorus or bridge, chorus, outro. Not necessarily in that order or containing all of those parts. Songs can be 30 seconds long or 3 hours long, but typically around 3:30 is considered "radio friendly." May I recommend checking out the song "Hook" by Blues Traveler as a quick lesson in writing a strong hook for your chorus, and letting that carry the rest of your song. The entire point of the lyrics was that it basically didn't matter what he said or did in the rest of the song, because the hook brings you back. In fact, the break, where he's basically rapping, talks about burning cities to the ground, and other inane stuff, but it doesn't matter because the "Hook" brings you back. Use what you like for examples of how to merge different parts, good rules of thumb is that they should typically be in the same key, tempo, and time signature, but even those aren't hard and fast rules. Many songs change key, tempo and time signature, but that will make it more difficult for you when you start.