1. Make a list of just a few items for the next day
Make it short, and make it count. What's most important? Be specific, so you'll know for sure if the task was accomplished or not. I recommend making your list at the end of the day when you're not sitting at your desk with all the distractions that can make you lose your focus.
2. Assign a duration for each item
Decide how long you think each item will take. Most importantly, be realistic. Rounding up is better than rounding down. I use 15-minute increments.
3. Add them up
Once you've got times next to your short list of items, add up all the time. Is that number larger than the hours in your day? That's when you know your list isn't realistic, and you need to scale it back. Set yourself up for success by scheduling only what will actually fit into your day. Remember to schedule mealtimes and exercise, if that's part of your daily routine.
4. Stay on track
When you start your day, remember that every hour is accounted for, so stick with your plan and pick an item on your list to start with.
5. Celebrate your success
This step is just as important as the others. Acknowledge all you accomplished and give yourself a treat if you want to. You've earned it. Now you're ready to sail through tomorrow's list, and you know how to make a realistic timeline.
This technique has worked for me amazingly well. In fact, I'm using it right now! I realized I'd been letting the task of writing this newsletter slide (you haven't heard from me since May 12), so I knew I needed to actually schedule the time and make it happen. See? It works! I've had my most productive days using this process. I'm confident you can too. Let me know how it works for you.