Buy yourself a journal you'd like to write in. I saw one which I loved with, "Don't let yesterday use up too much of today." on the front. Perfect thought for the front of a journal for sure!
You have to write down every meal, what time you at it, and exactly what was in it. Some people will just write down "salad". But what was in the salad? Salad can get very fattening depending on the add-ins.
Journals make you see what you eat but also pattens for what you eat and when you eat it. I had a client a long time ago who ate junk every Tuesday night. When he realized that, he could see that it was because he had a co-worker he worked with on Tuesdays who stressed him out a lot. Knowing that helped him to not make that mistake.
But journals aren't just for food. Keep track of your exercise and your moods too. You'd be surprised how much your mood effects your food and exercise performance.
Journaling is the KEY to getting in a great shape. If you don't know what you ate, you can't make changes. If you don;t know what you did in the gym you can't push yourself harder the next time.
So go out today and buy yourself journal. You'll be happy you did!