THINGS TO KNOW:
1) No dogs allowed.
2) Go at high tide. When we got there around 1 PM, the tide was way out into the Sound, and we hardly got to see much wildlife, though we saw 4-5 bald eagles. At 4:45 PM, as we were making our way back, the tide was coming back in. So, my guess is either go first thing in the morning, or after 5 PM.
3) Bring water! There aren't a ton of shady spots, and if the sun is out, it'll beat you. Also, the salt air will really parch your throat, and you'll wish you had water. Trust me.
4) WTA says it runs about 5 miles roundtrip, but the ranger told us 4.2 miles. It's flat, mostly a boardwalk. You can easily wear sandals or flats.
5) Restrooms at the visitor center.
6) $3 visitor fee. If you don't have cash, they'll help you out inside with a credit card.