Most people have never knowingly seen Mercury, the innermost planet — so if you spot it, you're joining an elite club. And the best news is that the price of admission is nil. Mercury is actually extremely easy to see, as long as you know exactly when and where to look.If you live in the Northern Hemisphere and prefer to go out in the evening rather than before sunrise, then this March is your best chance to spot Mercury all year, for two reasons. It's Mercury's highest and longest evening apparition. In addition, Mercury happens to spend the week from Saturday, March 12th, to Friday, March 18th, within 5° of Jupiter. (That's half the width of your fist at arm's length.) And while you might be able to overlook Mercury alone, the pairing is absolutely unmistakable.
All you need is a clear evening and a viewing site with an good view down to the west horizon. The shore of a big lake (or ocean) would work well, as would the top of a tall building or hill. Note the spot where the Sun sets, and then start scanning above (and slightly to the left) of there for Jupiter. Jupiter may be visible immediately if the air is very clear, but it will be more obvious 15 or 30 minutes later when the sky is darker (though Jupiter will also be lower).
Once you've found Jupiter, look for Mercury near it using the diagrams here. These are by far the brightest objects in that part of the sky, so there's no chance of mistake. The only possible confusion would be incoming airplanes, which often hold a similarly tight configuration if you live near an airport. But airplanes will shift within a minute or two, while Jupiter and Mercury stay put except for their gradual descent toward the horizon.
Mercury appears higher each evening in March until the 22nd, while Jupiter appears ever lower. So by the end of that period, Mercury may actually be the more obvious of the pair, despite the fact that it's slowly fading. Starting around March 25th, Mercury plunges back toward the Sun, fades rapidly, and soon becomes hard to locate with the unaided eye.
In a telescope, however, the later part of this apparition is most interesting, because that's when Mercury grows into a long, thin, crescent. It's 7" wide and 50% illuminated on the 20th, 8" wide and 30% illuminated on the 24th, and 9" wide and 20% illuminated on the 28th.