When it comes to calcium, what we really need to ensure is that we are taking in more calcium than we are excreting. There are cultures around the world (primarily hunter gatherers, I believe) who routinely consume less than 500 mg of calcium (perhaps even closer to 300 mg) per day. Yet, they do not have nearly the same rates of osteoporosis that we do in North America. Ironic, isn't it, that we have some of the highest calcium intake in the world and yet also some of the highest rates of osteoporosis? A large part of the reason for this is that North American diets tend to be very acid forming. When our bodies become too acid, the body is forced to leach alkaline minerals (e.g. calcium, magnesium, etc.) out of our bones, teeth, etc. in order to regulate body pH. Although meats are uniformely regarded as acid forming, most vegetables and fruits are highly alkaline forming. As such, as long as you are eating enough veggies (which tends to be richer in calcium than fruit), you are very likely maintaining a healthy alkaline balance.
One of the best ways to test how well your body is likely to be absorbing and/or excreting calcium is to pick up some pH strips and test the acidity/alkalinity of your urine. This will give you a better idea of how well your body is likely to be absorbing the minerals that it is currently getting. If you are too acidic, then I would recommend tweeking your diet to make it more alkaline. If you are appropriately alkaline, then you will simply have to decide how important it is to you to supplement with calcium. There seem to be sound arguments both for and against calcium supplementation. I think that the decision to supplement or not is a choice that only you can make. If you do choose to supplement, I would recommend that you get a supplement with the highest possible absorption. Too much poorly absorbed calcium can cause problems in the body. The higher the absorption, the more likely it is that you will get as many benefits as possible with as few side effects as possible. I have only just discovered it, but EZorb looks like a really good one. AlgaeCal and New Chapter Bone Strength are a couple of the other high quality options that I am familiar with.
Here is a like that talks a bit more about Calcium and Bone Health:
I hope that helps. ;^)