It's important that anyone who lifts heavy objects as part of their job knows how to do this in the safest way possible.
Before carrying out a manual handling task, you should always make sure that it's completely necessary. If there's equipment you can use to take the strain off you, do it. But, if manual handling is required, you need to make sure you do everything in the safest way possible.
Firstly, always plan your lift. Know exactly what you're going to be lifting and where it needs to go. Plan your route, clear the way, and plan any rest stops you might need to make along the way.
Before lifting, you'll also need to get into a stable position. The best way to do this is by standing with your feet apart, one foot slightly in front to help you maintain your balance. If the load you're going to be lifting is on the ground, your foot should be to the side of it.
The next step is to get a good hold on the load you're going to lift. Wherever possible, hug the load close to your body, as this will usually provide more stability than just gripping it with your hands.
You need to start in a good posture: slightly bending your back, hips, and knees is much better than fully flexing your back (stooping) or your hips and knees (squatting). It's also important to make sure that you don't flex your back further during the lift. This can happen if you straighten your legs before lifting the load.
During the lift, and especially while your back is bent, try to avoid twisting or leaning sideways. Your shoulders should always be kept at the same level and pointing in the same direction as your hips. Turning by moving your feet, rather than twisting your body, will also help to prevent you from getting injured.
Also, you should always move smoothly while handling a load. It shouldn't be snatched or jerked around, as this can make it harder for you to keep control of the lift. You should only ever lift loads that you can manage, too. Over-exerting yourself will only make the task far more dangerous and, if you're in doubt about whether you're able to lift a particular load, seek advice from your manager or employer. Finally, if specific positioning of a load is necessary, don't feel like you need to do everything in one go. It's usually much safer to put something down in a way that's comfortable, before sliding it into the desired position