The hardest part of pop arrangement which I have the most trouble getting others to understand is that the song should be an inclined plane, starting and a low point and building to a climactic crescendo, so to speak. If the last verse is played just like the first verse you're doing it wrong.
Boy if I could like this 100 times I would! There's a reason that the harmony vocals don't come in until maybe the second verse or chorus. There's a reason it's only one guitar and drums at the beginning then other parts come in. I always say keep it sparse at first then slowly build.
It depends on the tune, but I wouldn't follow that on every song. For example, Hit Me With Your Best Shot goes into a sort-of offbeat verse after the guitar solo, and the bass drops out of the chorus until the end. Or a song like Lover, Lover that ends acapella. The most important thing for playing 3 chord Pop is dynamics. The songs are very simple chord-wise, so you have to change it up in order for it not to be repetitive. If you just chunk out the same 3 chords the same way for 4 minutes, the song will sound like a lame Pop song. But, if you play it with conviction with some type of arrangement that has some dynamic changes, the audience will be eating out of your hand.