Throughout Capitol Hill, one can find many signs gently reminding dog owners to clean up after their pets. Here's a treasury some of the best ones I've seen, ranked from least to most favorite:
this lovely website!)
Folger Shakespeare Library. Appropriately enough, there's quite a "literary" flair to this sign: not only do we get some unusually authoritative word choice here ("police your dog," rather than a more colloquial "scoop the poop"), but the sequence of verbs also provides an elegant litany of actions: leash, curb, and clean.