Well, it certainly was a few decades ago when I was in my twenties. I was in Washington D.C. as tourist, walking around, seeing the sights. Having been educated in a typical U.S. public school of the time, I thought to myself, "Gee, as long as I'm here, I should visit my representative's office." The security situation was probably different then. I just wandered around the building, found his office, walked in, and announced myself as resident of his district. He wasn't physically there at the time, but I was welcomed and given a tour and chatted with a staffer.
An in-person meeting is the best way. If you figure that an e-mail is worth X, then a phone call is worth perhaps 100X, and an office visit is probably 10000X. Politicians do actually want to know what people care about, and the amount of work you do to get in touch definitely factors into how representative they think your opinion may be.
I was nobody - just a kid - but I was voter.