Where to practice riding a bike in Cambridge or Somerville

Fields provide a pretty soft cushion (not from the grass but the dirt, which does actually have some give to it) and there's no abrasion risk like on pavement. It's where groups of competitive cyclists sometimes practice contact drills for these reasons. Astroturf fields are especially soft due to the rubbery bits, but you shouldn't ride on them if you're on a 23 or 25mm tire.

Don't go on paths until you're able to ride smoothly in a straight and predictable line; the bike path is just like a road, only for bikes, and there will be people going fast on them. They'll probably give you a wide berth if they can or slow until it's safe to pass, but you have a responsibility as well.

Practice trying to turning your head without turning the bike, which is what naturally happens. Turning doesn't come from turning the handlebars, at least not at any appreciable speed. Turning comes from leaning, and on a road bike, with your hands on the hoods or in the drops, you can initiate a turn just by leaning more weight onto one hand or the other, instead of pushing or pulling. Stopping the turn is a matter of shifting weight back and getting the bike back directly under you.

As you get more stable, go to a parking lot where there are landscaped islands and carefully practice figure eights.

Lastly: learn how to stop properly. That involves, most of the time, using your FRONT brake. If you brace yourself, you will NOT go over the handlebars. If you allow your body to move forward relative t the bike, you WILL go over the handlebars. http://sheldonbrown.com/brakturn.html

(Ignore anything that's marked specifically as being from "John Allen" - he's a know-it-all douche.)