Deadlines are the chronological equivalent of a budget. By setting aside a portion of time to complete a task, goal or project in advance you avoid over-spending. Deadlines can be helpful but they can also be a source of frustration if set improperly. Here are some tips for making deadlines work:

1. Use Parkinson’s Law – Parkinson’s Law states that tasks expand to fill the time given to them. By setting a strict deadline in advance you can cut off this expansion and focus on what is most important.
2. Timebox – Set small deadlines of 60-90 minutes to work on a specific task. After the time is up you finish. This cuts procrastinating and forces you to use your time wisely.
3. 80/20 – The Pareto Principle suggests that 80% of the value is contained in 20% of the input. Apply this rule to projects to focus on that critical 20% first and fill out the other 80% if you still have time.
4. Project VS Deadline – The more flexible your project, the stricter your deadline. If a task has relatively little flexibility in completion a softer deadline will keep you sane. If the task can grow easily, keep a tight deadline to prevent waste.
5. Break it Down – Any deadline over one day should be broken down into smaller units. Long deadlines fail to motivate if they aren’t applied to manageable units.
6. Hofstadter’s Law – Basically this law states that it always takes longer than you think. A rule I’ve heard in software development is to double the time you think you need. Then add six months. Be patient and give yourself ample time for complex projects.
7. Backwards Planning – Set the deadline first and then decide how you will achieve it. This approach is great when choices are abundant and projects could go on indefinitely.
8. Prototype – If you are attempting something new, test out smaller versions of a project to help you decide on a final deadline. Write a 10 page e-book before your 300 page novel or try to increase your income by 10% before aiming to double it.
9. Find the Weak Link – Figure out what could ruin your plans and accomplish it first. Knowing the unknown can help you format your deadlines.
10. No Robot Deadlines – Robots can work without sleep, relaxation or distractions. You aren’t a robot. Don’t schedule your deadline with the expectation you can work sixteen hour days to complete it. Deathmarches aren’t healthy.
11. Get Feedback – Get a realistic picture from people working with you. Giving impossible deadlines to contractors or employees will only build resentment.
12. Continuous Planning – If you use a backwards planning model, you need to constantly be updating plans to fit your deadline. This means making cuts, additions or refinements so the project will fit into the expected timeframe.
13. Mark Excess Baggage – Identify areas of a task or project that will be ignored if time grows short. What e-mails will you have to delete if it takes too long to empty your inbox? What features will your product lack if you need a rapid finish?
14. Review – For deadlines over a month long take a weekly review to track your progress. This will help you identify methods you can use to speed up work and help you plan more efficiently for the future.
15. Find Shortcuts – Almost any task or project has shortcuts you can use to save time. Is there a premade library you can use instead of building your own functions? An autoresponder to answer similar e-mails? An expert you can call to help solve a problem?
16. Churn then Polish – Set a strict deadline for basic completion and then set a more comfortable deadline to enhance and polish afterwards. Often churning out the basics of a task quickly will require no more polishing afterwards than doing it slowly.
17. Reminders – Post reminders of your deadlines everywhere. Creating a sense of urgency with your deadlines is necessary to keep them from getting pushed aside by distractions.
18. Forward Planning - Not mutually exclusive with backwards planning, this involves planning the details of a project out before setting a deadline. Great for achieving clarity about what you are trying to accomplish before making arbitrary time limits.
19. Set a Timer - Get one that beeps. Somehow the countdown of a timer appears more realistic for a ninety minute timebox than just glancing at your clock.
20. Write them Down - Any deadline over a few hours needs to be written down. Otherwise it is an inclination not a goal. Having written deadlines makes them more tangible than internal decisions alone.
21. Cheap/Fast/Good – Ben Casnocha in My Start Up Life mentions that you can have only have two of the three. Pick two of the cheap/fast/good dimensions before starting a project to help you prioritize.
22. Be Patient - Using a deadline may seem to be the complete opposite of patience. But being patient with inflexible tasks is necessary to focus on their completion. The paradox is that the more patient you are, the more you can focus. The more you can focus the quicker the results will come!

Extracted from : http://www.lifehack.org/articles/productivity/22-tips-for-effective-deadlines.html