Every week or so, take a few minutes to delete your temporary photos, and back up your 'keeper' pics in the Cloud. Then turn that baby off (power it down completely) and get to work.
You'll need a pair of pointed tweezers, a microfiber cloth, and a small brush (like a toothbrush, but not yours), or a can of compressed air. You'll also need to take your phone out of the case.
First, use the pointed tweezers to clean the lint and debris out of the charging port. I can't tell you how many times people swear there's nothing in their charging port, only to have the tech pull out enough lint to stuff a throw pillow. If your phone isn't charging, this is the most likely culprit, yes, even more likely than that sparking charging cord you bought at the dollar store.
Sweep that tiny brush across the speakers a few times. You aren't trying to get under the gum line, here, just brush away the dirt. Some phones don't need this, but for the purposes of these instructions, I'm assuming everyone works in a coal mine.
Some people forgo all of the above steps (except the powering down) and use a can of air to blast everything out, which also works, I'm told.
Last of all, use the cloth, LIGHTLY dampened, to wipe off your phone. You know how you use a damp sponge to wipe off your counter? Not that damp, just damp enough to not be dry. Now that you've gone to all the effort of backing everything up and cleaning, there's no reason to cause water damage.
Use these tips with good judgement and at your own risk.
P.S. While you have it off, clean the case, as well!