Buy a day-planner and use it. Write down any appointments, or important tasks you have. Use the calendar to schedule what time of day you will work on each task.
Plan your day one week in advance. If you wait until the morning to plan the day's itinerary, you will likely forget something. Plan your overall goals and meetings at the beginning of each month, and then make adjustments at the beginning of each week. Each morning, simply review your planner and make any needed last-minute changes.
Keep your final goal in mind. If you have a big project to finish by next month, start by writing down everything that needs to be done to finish that project, and then schedule your daily time accordingly.