First, lessen salt intake. Avoid sugary treats as well because they are also usually high in sodium. Salt makes you retain water and it's something you really don't want happening, pregnant or not.
And if your pregnancy isn't a high-risk one, or you have your OB's go signal, get a massage (light/pre-natal) regularly. Massage has been proven effective in reducing edema as well as helping with the pain (and at the third trimester, a woman usually deals with back and hip pain from carrying all that extra weight).