How can i prevent injury when lifting?

The best way to avoid lifting injuries is to actually avoid lifting!! 

Unfortunately, that is not a viable answer for most, so here are some basic tips:

1) Plan your lift - once you have lifted the object, how far do you need to carry it, how high do you lift it, and what obstacles are in your way.
 
2) Get help if possible, especially for heavy and awkward shapes.
 
3) Make sure you keep your bum pushed out from you, and your back as straight as possible while lifting. Legs should be spread a reasonable distance apart, and knees slightly bent to cushion the lift. Always suck your tummy in tight before attempting the lift, to help activate your core strength, which will protect your back.
I would recommend searching on the net for pictures on proper “dead lift” technique, as this shows great lifting technique.
 
4) Never bend forward and twist the spine.
 
If you hurt yourself, book in for an assessment ASAP, the quicker the treatment, the better the outcomes. 

The best way to prevent injury when lifting is to maintain a good level of fitness and have some good core and pelvic stability, while lifting. Taking care of things like preparing the area well, not making jerky movements and certainly not biting off more than you can chew or lifting greater than you are capable of are things to think about. But on the whole, we see lifting injuries a lot less in people who have maintained a good level of fitness and some good core and pelvic stability.

There is a correct way to be lifting up heavy objects. Generally you want to hold the object close to your body and stand with the feet-shoulder width apart. You want to keep your back nice and straight, keep the stomach muscles turned on. Bend at the knees, instead of bending at the back, and lift up with the knees. If you Google ‘correct lifting posture’, a lot of images will come up of the correct way to lift, and they are all really quite good. The reason why we do not want you bending forward from the back is that when you bend forward, the spaces between the vertebrae open and this gives discs no protection, and allows a weak or damaged disc to bulge backwards. This can then cause pressure on the nerves, and again, cause pins and needles, numbness, or tingling in the hands.

The best way to prevent injury from lifting is to make sure you know how to activate your core stabilizing muscles before going into the lift. Keep the load close to your body as the further away from your body you hold the load, the heavier that load is going to be. Use your legs as much as possible rather than lifting with your back, especially when lifting something from the floor and remember if it’s too heavy to lift on your own, get someone to help you out. To learn how to correctly identify and activate your core stabilizers consult your physiotherapist.

I agree with all my colleagues above. I would like to add a useful tip is - if you don't know exactly how heavy the box or whatever you're lifting is, nudge it with your foot first, so you can get an idea of its weight and prepare yourself to lift it.

When lifiting we typically have to bend.  Before lifting it's a good idea to stand, put your hands at your waist and lean backwards - ie arch or bend backwards as far as possible.  This helps to counteract the bending or flexion you are about to do when you lift.

As an exercise physiologist this topic comes up a lot! The key more most people is flexibility (or lack of) through the posterior chain (glutes/hamstrings/calves) and the strength of the core:hip connection.

If you're interested I wrote a small article about squatting technique entitled DANGER! SQUATS!

Can see that HERE

That is a good read however the key take home message is lift within your capabilites and concentrate of the hips and back flexibility/strength