Many people have their chair too high.

Adjust your chair to this height now.

If the undersides of your thighs are now compressed, you need either a footrest or a lower desk. Most desks are a standard height of 710 mm or so (standardised before computers) so a large proportion of people will benefit from a footrest. A footrest can be bought, or made from a box, board, cushion or a piece of stiff foam. It doesn't need to be angled unless you wear heels or have it a long way away.

Adjust the height of the monitor so that you are looking horizontally to slightly down at it. Your head should be in balance on your neck most of the time, while your eyes look slightly down. Generally this means having the top of the visible area at eye height, when you are sitting upright.

Many people have their monitor too low.

You can raise the monitor on anything suitable that you have to hand, it doesn't need to be an adjustable monitor arm.

Adjust the angle of the backrest, and/or the length of the bottom-cushion, so that your back is supported in your work position, and the bottom-cushion is not too long for you.

If you can't sit fully back and upright without the back of your knees hooking the front of the seat, you need a different chair with a shorter bottom-cushion.

Adjust the backrest height so that it supports the lower back

Many people set the back support too low.

Sit very upright. If the shape of the backrest does not fit fully into the small of your back, you would probably benefit from adding a back support.

Move your chair forwards or backwards so that when typing your elbows are vertically under your shoulders. If you cannot get close to the desk because the chair armrests hit the edge of the desk, either change the chair or remove them with a spanner or an allen key. If necessary ask for help from your health and safety representative or DSE assessor.

Fixed-height armrests are generally too low, encouraging you to slump down to them. Adjustable-height armrests are usually shorter and will let you get close enough to your desk while offering valuable support taking some of the weight of your arms off your shoulder and neck muscles.

Short but fixed armrests can be raised by wrapping foam round them, or adding a layer of foam and wrapping fabric round. Don't be surprised if you need to add up to three inches of height in order to have elbow support when sitting upright.

Check the distance of the monitor. For most people to view the screen comfortably it should be about 22-26" (55 - 65 cm) away, so that your eye focus muscles do not have to work too hard.

If you are sitting much closer than this, consider if there is a problem with your eyesight, the screen quality or settings, or the desk depth. If you are using an old-style CRT monitor, usable desk depth can often be increased by pulling the desk away from the wall and allowing the monitor to overhang at the back.

If funds permit then replacing an aging CRT monitor with a new LCD-TFT screen will bring several benefits - more distance, more desk space, better clarity, a larger screen area, and no more flicker or radiation.

Check the side-to-side position of the monitor - it should be directly in front of you.

Don't put the monitor in the corner - either it will be hard to get close enough to the keyboard, or you will be twisted and your back and neck may develop problems.

Sit close to the desk and don't put things between you and the keyboard except a gel wrist rest - your elbows need to be vertically under your shoulders. Don't automatically deploy the keyboard's rear feet - you only need them if your elbows are below desk height. If you rest your wrists on the table when you type you should use a wrist rest.

Position and use the mouse as close to you as you can. Aim to have your elbow vertically under your shoulder, and right by your side or on the armrest.

If your mouse tends to stray away from you during the day, try making your mouse mat smaller (most can be cut easily) and sticking it down in the correct position with double-sided tape or blu-tak.

If possible, or at all costs if you develop any sensation in your mouse-side shoulder, use a narrow (84-key) keyboard so that you can have your mouse closer.

If you often refer to documents whilst typing use a document holder. This should be positioned at the same height and distance as your monitor. If you look at the documents more than the screen put the document holder directly in front of you and the monitor to the side.

Eliminate any glare or reflections on your monitor. Try closing blinds and changing the position of the workstation so that the monitor is at right-angles to the window.

Turn off overhead lights unless you really need them, using a tall desk lamp for reading. You can reduce reflections from overhead lights by raising your monitor then tilting it down to make the screen vertical.

Position any additional equipment e.g. phones, paper trays, reference material in accessible places. Try to avoid reaching and twisting. Investigate storage facilities and desktop accessories to help you organise your workstation better.

The temperature and the humidity should be adjusted so that they are comfortable.

Eliminate any uncomfortable draughts.

If you are experiencing any discomfort during your sessions at the workstation, stop and seek advice.

If you have discomfort that does not completely disappear overnight then treat it as an emergency - stress damage is now accumulating faster than your body can repair it, so you must break the circle otherwise you will very quickly develop a lasting injury. Try to change something this morning to reduce static muscle loads.

If you're at Loughborough University in the UK you can get advice from your health and safety representative or DSE assessor.