One of the greatest things about the iPhone is how it has completely changed the way we communicate, interact with the world, and even work. One of the things that make that possible is all of the apps that help you be more productive. Sometimes, I feel like I've tried all of them. I've even reviewed a lot of them for this column. 

Over time, however, I've come to realize something important. The most useful tool for being productive isn't an app on your iPhone or Android smartphone. 

I'll get to what I think is the best tool for being productive, but I think it's important to clarify something first. A lot of us spend more time than we should trying to figure out how to be more productive, instead of just doing the stuff we need to do. Which is literally the definition of being productive.

We'll try out new systems and apps, and try to figure out some secret way of squeezing out just a little more "productivity" from our day. In reality, the overall return is rarely worth the opportunity cost of playing with iPhone apps all the time. That doesn't mean there aren't some great productivity apps on the iPhone. 

Frankly, I'm a big fan of Things 3. There's also OmniFocus, ToDoist, Evernote, Reminders, Trello, Asana, and even Microsoft To Do. All of them are very good at what they do. In my opinion, however, none of them are nearly as effective as this one simple tool.

For me, the most useful productivity app is one we've all been using since long before we had an iPhone. It's a piece of paper. 

Now, I know a lot of people like to make lists on paper. And paper planners and organizers are a very big business. Personally, I just use a small notebook to collect ideas, tasks, and notes throughout the day. It's very effective, and the act of writing things down on paper helps my brain to think through what I need to do, and be intentional about how I plan my day.

That's not what I'm talking about, though. In this case, I'm talking about one specific piece of paper that has single-handedly made me more productive. 

I keep a piece of paper near the bed so that, before I lie down to fall asleep, I can dump thoughts onto the paper instead of letting them rattle around in my brain. Then, I organize my thoughts into a list of the things I want to accomplish in the morning. 

That way, when I wake up, I already know what I want to work on. I don't have to waste that time trying to figure out what to do--I've already made a plan. I find that it's very hard to context switch between figuring out what to do and actually doing it. 

For example, I try to think through what I need to research in the morning, what articles I'm going to work on, and whom I need to contact. Then, when I wake up and start to work, I can dive into the list I made the night before, instead of trying to remember what I was thinking about the night before. I've already filtered through and organized those thoughts into something I can act on.

I also keep the paper near the bed so that as stray thoughts creep up on me, I can quickly write them down. Getting thoughts out of your brain helps you fall asleep much faster because you're no longer using energy and brainpower to try to remember them.

Could you do the same thing in an app? Yes, of course, you can. But which app? There are hundreds, if not thousands of choices. Some of them are great for scheduling tasks. Some of them are really good at repeating tasks. Some of them are really good at reminding you when something needs to be done.

Besides, I happen to find that I think better with pen and paper. Plus, there's another important benefit. I happen to be most productive from 5 a.m. to 9 a.m., so getting a good night's sleep is pretty important. Doing a brain dump on that piece of paper helps me get to sleep faster, which means I'm at my best when I wake up in the morning.