A basic acrostic is a poem in which the first letter of each line spells out a word (sometimes a name, like this example from the Lewis Carroll). Acrostics can also become more complex (by having the last letter spell out a different word) but we can keep it simple.
(Note: mnemonics are a very simplified form of acrostic, in which there is only one word in each line. You can totally write a mnemonic if you'd like!)
Here's my poem for the day:
After a Horrible Day, the Poet Gives Thanks
Later, evening falls and my chest Expands in anxious contractions X-rayed through and through, I cannot feel - the very depth of core. Exception eludes me.
Light breaks through electronically Over and over, brightening the room. Very soon we will spoon, Evolving into one creature Soaked skin sweating onto the sheets.
My love, you've proven your worth! I escape anxiety in your arms Killing my exhaustion, breaking the bounds, Effervescent in satisfying relief.
Acrostics lend themselves to love poems. I've written more than a few poems to my husband (who I refer to as M in this blog) in this form.
A note on the capitalization: while it Is no longer standard practice to capitalize the first word of each line of most free verse poems (though you can do so with any poem, if you choose to follow the older style), with acrostics, I do tend to capitalize the first letters to give emphasis. You absolutely do not have to do that! You can capitalize or not capitalize however you'd like.
[And further note that in the years following my writing this prompt, I have mostly stopped capitalizing the first line in acrostics, for no real reason at all. It's just my style these days.]