Caffeine seems so simple, even if you're a veteran user. You drink it, you get amped up for a short period, and you inevitably come down a bit when it wears off—or so you think. But caffeine is a more subtle substance than we give it credit for. Knowing how it works on your body and brain, and how it is most effective, can give you an edge at concentrating, while still keeping the jittery edge off.
The best way to get the most from caffeine is to start from scratch. There are a lot of factors that play into how a dose of caffeine affects you, but there's no stronger factor than the tolerance you've developed, morning after morning. Give yourself a week to 10 days to recover, scaling back slowly if necessary, then start fresh with coffee as an occasional, smart pick-me-up.
Note: Biological and genetic factors also play into your caffeine interaction, and it may not be for everybody. This is just a starter's guide for those who want to stop feeling like one cup isn't enough.
Yes, you probably have a caffeine tolerance. Learn to adjust it.
Patients waking up from surgery in which they went under anesthesia often wake up with a killer headache. Doctors used to blame their own knock-out juice, until research showed how effective a post-surgery cup of coffee could be. Most of us are used to having our regular coffee or tea, occasional sodas, and bits of chocolate, but when asked by doctors not to eat or drink anything for long stretches before surgery, then sleeping off the drugs, your body wakes up to a system without any caffeine, and it's a mite unhappy.
Knowing this, and having days or weeks where you know you're going to need reliable energy boosts, try to keep yourself caffeine-neutral and wean yourself from dependency. It takes between a week and 12 days to build up a tolerance and dependency on caffeine (even at just one cup a day), and an average of 10 days to work it off. Once you're past the rough mornings and headaches, you're able to strategically deploy the stuff when you've got a big day ahead and need better attention and memory performance. But keep in mind ...
Caffeine unlocks your potential energy, it doesn't create energy
Stephen R. Braun, author of the excellent explanatory tome Buzz: The Science and Lore of Alcohol and Caffeine, told me in an interview at Lifehacker that caffeine's effects were best described as "taking the chaperones out of a high school dance." Caffeine does its magic not by directly stimulating your cells, but by being extremely similar to adenosine, a cell by-product that your body monitors as a kind of gauge for exhaustion. Caffeine's molecules plug up your receptors for adenosine, so your body stops getting signals that it's tired.