Memorizing poetry

Of those choices, I'd say "small bits". I start with the beginning and memorize the first line or two, and as I become comfortable with it, I add another line, and then another, and so on.

I also continually recite the poem to myself, at every slack alone time, like waiting for the bus or showering or driving. The more you repeat it, the better it gets into your memory.

 

Re-reading frequently, and reading out loud when you do so, in my experience tends to help a lot. Writing out the piece you want to memorize in longhand, just copying it out of a book or whatnot, helps way more than you might think.

As @Baraka_Guru says, poems with consistent meter and rhyme scheme may be easier to memorize; but even with blank verse or free verse, it helps to treat the piece like a monologue: visualize something for every word or phrase, so that you can speak it naturally, and not in the singsong of rote. Alternatively, one can actually embrace the singsong aspect, and change tones for different phrases, so that when one recites the poem, it is more like chant than like speech. The musicality of the changing tones can be like a mnemonic, aiding in memorization. That's one of the ways bards aided memorization of epics in ancient times.

 

It also helps to notice patterns, and specifically take note of what makes similar sections different.

For example, there are two consecutive verses in "The Raven" that start with the same line:

The first of the two verses have two and a half more lines of musing about the Raven, before he starts asking. He gets to the question much more quickly the second time.

Knowing that helps prevent confusion while reciting this passage.