Choose your journal. It can be a tape recorder, a gorgeous, bound journal or an old spiral notebook. You can even journal on a computer word-processing program. Find the way that works best for you and stick with it.
Remember that your journal is not graded. Since you are the only one reading it, you can have fragmented sentences, poor sentence structure and all the misspelled words you want. The feelings and expressions are what is important, not whether they are grammatically correct.
Structure the journal however you want to. You can have a new entry for each day or just randomly write whatever comes to mind. You can also add items to the journal, such as concert tickets, cocktail napkins or other items that represent important memories.
Write consistently, whether it's every day, once a week or monthly. If you let yourself get out of the habit of journaling, it becomes more difficult to get back to it.
Keep it where you know it will be safe. This confidence will allow you to be more open in your writing than if you think the information is vulnerable.