"A sad, shabby truth about me: I can't tell if poetry scans. Truly. This presented a bit of a problem in college as I was, um, training to be a poet. I could wing a certain amount (believe me, there is plenty about myself that fills me with self-loathing, but I have to say I'm a glorious winger) still, I knew at some point ahead, in some graduate seminar, the fraud was going to be revealed. It was a little like showing up day after day for a gig at the symphony without the ability to read music, just a rough ability to saw on your violin.
The worst part is that I've had scansion explained to me many times, by several good teachers and professors and helpful friends. And as these people were explaining it to me, I'd experience a glimmering of understanding that would extinguish as soon as I went back to reading the poem by myself."
Nah. You would have been fine. No else knows how to "scan" either. (Especially the ones who THINK they know).
Seriously, though, this shows a curious attitude I've seen in some students in the past: the attempt to keep knowledge at an arm's-length rather than plunging into the subject-matter, making it their own. I had a student studying for his PhD exams who was speaking one day of the "literati" in the third person. I had to stop him and say: the "literati" --eres tú. That is, if you're not defining yourself as part of the group, what are you doing here?
The first thing you need to know about scansion is how to speak your own language. We already know where the accents go, because we know how to speak English. If you can't walk you'll have a hard time dancing. Assuming you don't put the accent on strange syllables when speaking normally, the next step is to simply read ALOUD enough poetry aloud so that you start to instinctively feel the relation between the normal phonological patterns and the alternating weak-strong pattern of the meter. Lines vary a bit in how "obvious" this connection is:
"Of hand, of foot, of lip, of eye, of brow"
would be an example of a case where each "foot" is also phonological phrase. That's one extreme. Only if you expect every line to be like this will there be a problem.