We tend to equate productivity with working hard, but spending 10 hours a day chained to your desk may not actually be a good thing.

In order to work well you need to take a step back and think how you can manage your time and energy to best effect. It's about working shrewdly, not endlessly.

The so-called "80-20 rule" is central to this. Widely used as a tool for business, it says that 20 percent of time is used to produce 80 percent of results. And if you think about how many hours of a week you waste trawling through emails or randomly scouring Facebook, it makes a lot of sense.

The key is to know which activities produce your results, and focus exclusively on them.

It sounds obvious, but a healthy work-life balance with plenty of breaks and minimal overtime is also central to maintaining a creative, productive work ethic - something that can be easily forgotten in the relentless drive for achievement.

Belle Beth Cooper, content crafter at San Francisco-based social media company Buffer, says: "One of the things I love about the culture at Buffer is the emphasis on working smarter, not harder. Our team is all about getting plenty of sleep, exercise, and recreation time, so our time spent working is as productive as it can be.

"Working harder can be an easy habit to slip into, though."

Here are five simple and effective ways to make the most of your working day, to get more done in less time. Three cheers for leaving the office on time!

Start off by ranking the most important things you need to get done on any given day. Write them down in order of importance and cut out anything that's not essential or time-sensitive, to work out exactly where your priorities lie.

In order to be really efficient, you should try and cut this down to three key tasks. The best to-do lists are minimal because they siphon out easy, low impact things to do and just stick to the big picture (you can assign the lesser tasks to another bulk of time, perhaps at the end of the week, or delegate them).

"This is where the rubber meets the road on focus and prioritization," says Forbes business expert Vanessa Loder. "If you could only do one thing today to move your business forward, what would that thing be? Make this the #1 item on your To Do list."

Good lists also concentrate on today only: if you think about everything you need to do ever, it may become overwhelming and it muddies your focus. Divide longer-term projects into workable chunks and allocate a section to tackle each day.

Once you've worked out what you need to do, set deadlines for doing it. Studies have shown that we work within the time we allocate ourselves; so if there is no time limit, we let projects drag out forever. Similarly, if we allocate ourselves a deadline that is too wide, we end up making a big deal out of something that could be have been completed fairly quickly and painlessly.

The deadlines you set should be realistic, but also rigid. Divide activities up into 30, 60 and 90 minute slots. After 90 minutes, attention wanes and energy levels tend to dip, so it's a good idea to take a break, even if you return to the same task afterwards.

Sticking to a deadline will force you to stay focused and disciplined, with no time for procrastination. As you start to introduce cut-off times to your working day, keep track of your progress to see where and why you end up distracted - then work out how to get rid of these triggers.

"Tracking your progress in this way has been proven to increase self-control because you’ll be exposed to the work you’ve actually accomplished, and not the (inaccurate) assumption of work you might construe in your head," says marketing strategist Gregory Ciotti.

Read: five things all productive people do at the end of every working day

It's energy, rather than time invested, that has the most impact on productivity. So rather than spend ages languishing over a particular project in the vain hope that it will somehow come to an end, devote your energy to it in short, intense bursts with regular breaks in-between.

When you have a break, make it a proper rest. And when you work, make sure you are fully focused. Switch off your phone and email if you can and ask your team not to interrupt you if they can help it. Then get your head down and stay on-task.

Working like this is a far more effective way of getting things done than if you're simply trundling on - neither fully focused, or fully rested.

"Work in short bursts so that you don't get mentally or physically distracted," says Clare Evans, author of Time Management for Dummies. "Give yourself mini-targets for what you're going to achieve in the next hour and then take a break. When you have a lot to do or you're feeling overwhelmed, you need to prioritise. Do important tasks before they become urgent and avoid time-wasting tasks. Get support, if you don't have the skills to do a particular task, ask someone else or delegate to someone who does."

Trying to do too many things at once can make you less productive, more stressed and less intelligent (or "work-stoned", as experts refer to it). In fact, studies have shown that people who multitask waste up to 40 percent more time than those who focus on tasks individually.

"The word multitasking is inaccurate because you are not performing multiple tasks," says Dave Crenshaw, business coach and author of The Myth Of Multitasking. "You’re actually switch tasking – switching rapidly back and forth between each task. As you do this you pay tiny 'switching costs'.

"When you multitask you are slowing down hourly. Ultimately tasks take around half to twice as long to do."

In order to avoid this, you need to map out time for particular tasks - including checking email - at a specific interval every day. Contain that task to its exact time slot and don't allow yourself to re-visit it when you're doing something else. When you've got a project on, create the head space to do it in by turning off distractions and taking regular breaks. 

Read: the great multitasking myth - why drowning in a sea of post-its is posing a serious threat to our health

Taking regular breaks is the most important factor to achieving more in less time. Without space to recharge, you end up sluggish and lacking in motivation, with a high chance that you will simply slump your way through the day. You're at your least effective after hours and hours of working without pause.

Research has shown your brain can only focus for 90 to 120 minutes at a time before it needs a break. After 90 minutes, we move from a higher to a lower level of alertness, in a pattern that's known as the ultradium rhythm. 

Try to schedule in breaks of at least 15 minutes throughout your day, and make sure it's proper time out, taken away from your desk (a brisk walk is a great way of refreshing your mind). It sounds like a lot but it'll pay off in the long haul, in terms of keeping you fresh, dynamic and motivated.

Similarly you need to know when to stop and quit while you're ahead. Don't be tempted to plug away at a project into the early hours, unless it's a one-off exception. Create a cut-off time in the evening to go home and relax and then take another shot at it the next day. Longer sleep hours, more hours away from the office and longer, more frequent holidays have all been shown to have a positive impact on job performance and health. 

Look after yourself, and your productivity can only increase.