In the first stanza of "I Wandered Lonely as a Cloud," Wordsworth puts himself in the place of a cloud, and states that he (the cloud) "wandered lonely...o'er vales and hills" and then down below him, saw an entire "crowd" of daffodils. Simply put, a cloud is wandering, or floating over some hills, when it comes upon a field filled with daffodils. It is a pretty straightforward stanza, and sets up the rest of the poem.
Wordsworth uses personification to compare the daffodils to a "crowd". Personification is where you give inanimate objects human-like traits, and daffodils can't crowd together like humans can. Crowding implies action and choice. He continues with personification when he says that the daffodils are "dancing" in the breeze; only humans can dance, so he is personfying the daffodils there. Check out the last line of the second stanza also, where the flowers are "tossing their heads in a sprightly dance." This too is personification, and that continues throughout the entire poem, so watch for it.
Wordsworth also uses a simile in the poem (comparing two things using like or as); the first line of stanza two has him saying the flowers are "continuous as the stars that shine." Later, he uses a metaphor when he compares the flowers to being at the edge of a bay, jumping and jostling on the "waves" of the wind.
Those are just a few techniques in the poem; I hope that those thoughs help. Good luck!