The short answer is that the secondary stress gets elevated to conform to the meter:
the OC / to PUS / is LONG / and BLACK
her DEC / la RA /tion STUNNED / the ROOM
That's not to say that you would put an exaggerated emphasis on "PUS" or "DEC", but the meter causes them to take more stress than they would take in ordinary speech.
As for anapests, some "strict" metrists avoid them, whereas others (Robert Frost, for example) use them frequently in iambic verse. It's all a matter of preference.
As for using a lot of long words in poetry, it all depends on the effect that you are trying to achieve. English is an amalgam of Latinate and Germanic languages. Most long words are of Latin derivation, whereas the majority of short, "business" words are Germanic. Latinate words tend to sound more cerebral or intellectual. In poetry as well as in day-to-day speech, we use more Germanic words than Latinate, but poets often throw in a Latinate word here and there for emphasis or special effect.
Here's a short list of Germanic words with their Latinate equivalents (this isn't original to me -- I lifted it out of a book). Not all Latinate words are long.
ship/vessel
merry/ecstatic
life/existence
dream/illusion
sweat/perspiration
spit/expectorate
house/residence
love/affection
food/nutrition
light/illumination
bath/ablution
[My apologies: I posted this response before I realized that this is the Poet Lariat board. I think Ginger's question was directed to Robert Mezey.]
Caleb
www.poemtree.com
[This message has been edited by Caleb Murdock (edited August 14, 2001).]