Well a true and accurte reading is hard to come by even by professional with tons of equiptment (though they get pretty close). Most colleges offer it as a service so you can check into that.
As far as a general reading of your metabolism or the "home" way of doing it is by judging caloric intake vs. weight gain/weight loss. Using a BMR calculator like this
you can get a rough estimate of what your body needs when at a complete rested state. Then you add in general activity.
That gives you your rate when you include daily activity/exercise and so forth.
Using these formulas you can get pretty close to a guess. Then you test it out with whatever your goals are to see if it works out. Sometimes you may need to add a little or take away some calories to hit your right spot. Its all about listening to your body AND giving it enough time to adjust to any changes. For example if you were under eating for a long time you are going to have to rebuild up your metabolism to be at a healthy level and let your body work it out.