To all you innies out there (like me!):
It is very important to clean your belly button once in a while.
You will need a q-tip (or several) and baby oil.
1) Coat the tip in baby oil.
2) Clean your innie.
3) When the q-tip looks disgusting, use the other side.
4) Repeat until as clean as possible.
Don't rush this, as you might hurt yourself.
Extra tip: Avoid leaving soap residue on your belly button, and dry it after bathing ;)