Approved/safe methods and techniques are used when lifting a

Do not attempt to manually carry a load which you cannot easily lift and which you cannot see above and around. The maximum weight of load that you should lift is 20 kilogrammes,but as a trainee this may still be too heavy for you.
When you are lifting items from the floor always keep your back straight and bend your knees. Bending your back whilst lifting can cause back injury. If you keep your feet slightly apart this will improve your balance. It is always a good idea to wear safety gloves when manually lifting.
Hoists and jacks are available for lifting vehicles; hydraulic or chain-operated equipment is available for lifting engines; hydraulic devices are available to lift gearboxes. For moving equipment and heavy components you should have either a trolley or a sack-truck.
You are advised to seek the assistance of a colleague when moving a heavy load even when you are using lifting equipment.Car Repair Talk's forum.