Decide what you want to use your writing journal to talk about. It can be a single subject or a combination of several ideas. You can use your journal as a diary and write about what happened in your day at school, at work or even on a date. You can express your emotions and how you feel about a friend, a family member, a coworker, a boss---even your dog.
Decide what format you want to use. You can go the old-fashioned way and use pen and paper. Several book stores and shops have different journals for you to choose from. Or you can decide to do it online, in a blog format, using a free blog provider such as blogspot.com or wordpress.com. If you decide to write online, you should also consider whether or not you want other people to view and read what you write.
Once you decide what medium to use and what your topic will be, plan when and where you want to write. Do you prefer to wake up early and write while watching the sunrise, or do you prefer to look out at the moon at the end of the evening and write about what happened that day? It is important, in the beginning at least, to set out a specific time to write in your journal. This is to ensure that you make time to do it every day even if you don't feel like it. Unless you are very disciplined, it is easy to find other things to do ithat you think are more important. So make it a priority. Schedule a certain time each day to write.
If using a daily writing journal to track weight loss or food consumption, make sure to go ahead and review your entries at the end of each week to track your progress. Make goals in your journal for what you want to accomplish for the next week. Make sure you take your journal with you everywhere if tracking food consumption so that you can write down what you eat right away. This way you won't have to try to remember everything later.
Have fun with your journal. Do little drawings in it if you feel creative, add photographs, quotes you heard and liked, anything you want. Remember, this is your journal and indicative of you and your desires. Nothing you write in your journal should be off limits, feel free to express yourself and have a good time.