I avoided this trick for several years. I stated using one in October last year and found it very helpful and keeping me on track. What was also helpful was that I had to show my food journal to another person once a month. That kept me from the chocolate when I really wanted one.
If you search for food diary templates on the internet, you will find many choices from apps to downloadable, printable ones such as this one:
I like this template because along with lines to list your food intake, and a space to check off the number of glasses of water you drink each day, it also includes a place to list where and when you ate, how you felt before and after you ate, a review of how you felt each day, and behaviors that require your attention. There is also a line to add your weight each day. New studies have shown that contrary to previous advice, people who weighed daily lost twice as much weight as those who weighed only once a week.