Meter for dummies?

Please don't be scared of meter.  It's just like any other way to measure things.  Just like length is measured in centimetres (or inches if you're in that archaic non-standard world), meter is measured in "feet".  Meter types actually vary from language to language, because every language has different ways of accenting, so we can only really talk about English -- a language which has very definite accents on words.  Check the dictionary if you're not certain where accents fall in a word and it will tell you -- that's really all you're looking for when it comes to meter. 

Meter (or rhythm, in it's less defined form) is what makes a poem MOVE.  It's the measure of how fast or slow it's read, how it feels when you hear it, how to build emotion, mood, image... meter is the colour to fill in the lines.  Even free verse uses meter -- it's just not a regular pattern.  Without attention to meter you'll find that your poem "stumbles" or is "awkward" -- some people use meter innately, without even knowing what they're doing, and some have to really work on it.  Don't panic if you're in the second group.  It WILL come to you.  

Think of a musical score.  The strong stresses in a metric line are the ones that would fall on the beat.  The soft/weak stresses are the bits in between -- you can't do without them but they're not driving the tune.

Take a metronome.  Basically, it goes TICK-tock.  If you were to start your poetic line on the TICK, and just put two syllables per beat, you'd have a trochee.  TICK tock/ TICK tock/ TICK tock/ TICK tock...  But if you started your line on the tock, keeping to the two syllables per beat, you've got an iamb... tick TOCK/ tick TOCK/ tick TOCK/ tick TOCK... The trochee is more forceful to begin with but the line ends on a soft stress, so when you hear a trochaic line it's the beginning you remember most clearly.  The iamb starts out softly but the last stress on the line is a strong one, so you remember the close of the line more clearly.

It doesn't matter if you're tone deaf because this is the mathematics of music.  Metric feet are just units of measure.  You need to remember that a line of poetry is not the smallest unit, it can be broken up and you need to understand what each part is doing.  Maybe it's more like chemistry... once you know what it's made of, you can manipulate those molecules to form whatever substance you like.  Only with poetry, you can actually turn lead into gold.