I've been taking a calcium supplement for years. It was hard to get into the habit, but the tasty chewable ones make it easier. Turns out that I was taking calcium every day but not in a way that was most effective. When you take calcium, what you take with it and how much you take at one time can make a difference in absorption.
Calcium carbonate (the most common type in supplements) should be taken with food. But our bodies only have the ability to absorb 500 mg at a time. That means if you take the recommended daily allowance (1000-1300 depending on age), don't take it all at once. You will absorb more if you take 500 mg twice a day.
It also means that calcium supplements or multivitamins that contain calcium should be taken with foods that contain no or very little calcium. Taking a 500 mg supplement with a meal that contains 200 mg of calcium does not give you 700 mg since your body can only absorb 500 mg at a time.
And here's another thing to keep in mind: Iron and caffeine interfere with calcium absorption.
I'm revamping my vitamin schedule. I've missed a few doses, and I'm still trying to work out a schedule that I can stick with but at least my effort and money will result in stronger bones.