If the baking powder in your cupboard hasn't been used since last holiday baking season you might want to test it out to see if it's still good. Baking powder can lose potency over time, there is a simple test you can do to see if yours is still good for baking.
Put 1/2 a teaspoon of the baking powder in a small bowl, pour in 1/4 cup hot tap water. The more bubbles the fresher the baking powder, you want lots of activity otherwise dough won't rise sufficiently. If you're not sure what lots of activity looks like, try this test the first time on a fresh container so you can see what good activity looks like.
I tested mine so I could take the picture, very few bubbles so I need to toss it and start fresh, I should have known, the last few times I made cookies they turned out strange looking and kind of sunken in.