We were there for the 4th in 2002. It was HOT!

Traffic will be a mess during the parade.

They had pretty much locked down the Mall for the festivities that evening. If it is similar this year, allow time to get through security.

Bring lots of water, especially while on the Mall. Otherwise, if you can find any, you'll be paying like $5+ a bottle.

We sat on the Reflective Pool side of the Washington Monument.

As for Metro after the fireworks, fuggedaboutit.