Weight training and high intensity interval training (HIIT) are great ways to increase metabolism long after you stop working out.
In addition, there has been numerous studies showing that drinking Oolong tea daily increases your energy expenditure by the amount of polymerized polyphenols it contains. It tastes great too.
A tablespoon of ufiltered unpasteurized organic apple cider vinegar in a glass of water has also been shown to speed up metabolism and help in reducing weight. Be careful with this as the taste could be very offensive to your taste buds. Some sweeten this with a little bit of honey to make it go down smoother.