[There's not really a "Spolier Alert" for this post, but it's a little gross, so let's call it a "Spoiled Alert."]
I've found that when teaching Sam and Aidan to go potty, I taught them to think of the toilet as a target. Well, apparently that works for any age (from "Slate's What's New In..." column):
"A piece in the New Republic reveals that after an economist proposed etching a black fly near the drain of toilet bowls in a men's restroom at an Amsterdam airport, "spillage" was reduced by 80 percent—"It turns out that, if you give men a target, they can't help but aim at it." "
Personally, I prefer those little plastic mats that look like a dartboard, but to each his own.