To memorize the Russian letter И, think about it as the flipped English N.
Here is a mnemonic that can help: Russian И by itself means and, and N in English sometimes serves as a shortened version of and (like in rock-n-roll).
Pay attention that in hand writing И looks more like English U.
When И follows a consonant, the consonant becomes soft.
Practice in syllables
Words with this letter
Unstressed О sounds like А.
Practice with a worksheet
Practice the hand-written Russian letter И, as well as the syllables and words listed above, with this worksheet: download the worksheet.