So you'd like to submit an event for inclusion in the calendar? Excellent. Here are some pointers to make things easier for everyone:
If you have links to maps, directions, transit information, parking information, or anything else that will make it easier for folks to find you, please include them. Remember, you're trying to make it as easy as possible for the maximum number of like-minded individuals to find you. The more precise your information, the larger a turnout your event is likely to reap.
Please don't assume that your humble calendar maintainer is omniscient. While he can probably, given nothing more than a building name, track down map information leading to a location somewhere close to your intended gathering point, it's much better if you eliminate all opportunities for guesswork and error on his part by spelling it out.
Also, bear in mind, when planning, Don Marti's admonition that it's good to assemble protests a block or two from your intended target, and then march there en masse. Much more effective psychologically.