Mayhew's simple rules of scansion.

1. Forget the poem is in verse: simply mark where the major stresses lie.

2. Apply any phonological rules (e.g. the "rhythm rule"). Mark secondary stresses. Note the difference between "in love" and "eating on the way." In the first phrase the preposition has no stress at all. In the second, on has a secondary stress because it falls between two weaklings. Words like "secondary" have a primary stress and a secondary stress.

3. You're done! No, wait a minute. You can now compare these stresses to what you think the abstract metrical pattern is. You will find either a good match (i.e. most of the stresses fall where they should, or not. Are there extra syllables? Missing syllables? Inversions? The hardest to reconcile tend to be polysyllabic words at odds with the abstract paradigm. Read some Paul Kiparsky.

4. Reading poetry aloud for hours at a time, you will simply learn how to pronounce English more or less normally while at the same time feeling the abstract pattern of meter. I recommend Shakespeare, Paradise Lost, The Prelude, and anything by Dryden or Pope. Learning to scan single lines is pointless without this extended practice. Now practice speaking in blank verse:

It isn't very difficult, you know
since English tends toward regularity
of alternating strongs and weaks. My house...

It isn't hard to write verse. What's difficult is to write poetry in verse.