Sit down with your journal. If you don't know when to do this, consider taking time just after lunch or right before bed. Waiting until evening before you go to sleep is a practical time to journal because you can recount the day. The first day you start journaling can be very important because years later when you pick up your finished journal, you will be transported back to that first day. A date can hold memories and associations with your life and the period in time.
Date your entry (and all your entries). Dates are useful when you return to read your journal later or intend to leave your journal for others to read. Again these dates are important because they give the history of the world at the time you are writing.
Set your timer for 10 minutes. These 10 minutes should be uninterrupted minutes for yourself. Peace and quiet can help transfer your thoughts onto paper.
Start writing. If you are drawing a blank as to what to write for the day, write questions at the top of each page. Some journals include starter questions, but you can write the questions yourself too. Some examples: "What did you eat today?" "What did you dream last night?" "What is the most current news you have seen?" These questions are meant to provoke your thoughts.
Keep writing. Write until the timer goes off. Or keep writing if you're on a roll and have the time. If not, congratulate yourself for getting through the 10 minutes.