I can't emphasize enough how important it is to be mindful of what you are eating on a daily basis. Particularly if you are trying to drop some weight it's that much more important to your success. I've seen a direct correlation in the clients I've trained in relation to keeping a food journal and getting results...those who kept a journal would get results and those that didn't sometimes would get results, but most of time they didn't. It is such a huge accountability factor that in my opinion can't be left out of a fitness program.
You have to find what works best for you. Some like a journal they carry everywhere with them, others might type it up on a word doc at their desk, or use a certain software on their phone. One of my favorite ways to track calories is through an amazing free website thedailyplate.com that a friend told me about a few months back. It's super quick and easy. My favorite part is you can customize it to your goals and enter your daily exercise as well.
So weather you're just a fitness junkie or trying to lose a few pounds before swim suit season I highly recommend this little gem to help you get to whatever your goal might be.