Sounds silly to some, but many people are scared to do this and some people have been really hurt by not jacking up their car properly and taking the necessary precautions.
Think about it, do you want a car to fall on you, or do you want to damage your car when it drops to the floor without a wheel on ?
Follow the advice on this page and you should be able to keep yourself safe.
When will I need to jack up a car ?
- to change a wheel,
- to change brake pads,
- to check your exhaust,
- What will I need ?
You will need a ‘jack’ to lift the car and ‘axle stands’ for safety, and if you are taking the wheel off you will also need a ‘wheel brace’ (for removing the wheel nuts). Most cars come with a car jack and wheel brace like this ;
Typical Jack Supplied With Vehicle 
Typical Wheel Brace Supplied With Vehicle. If your car did not come with a jack and wheel brace then you need to buy some. Most motor factors sell them, and you can get good deals online. Check out Amazon and eBay for some of the best deals.
There are different types available, click on the images for more info ;
If you are using the jack that came with the car, it should be designed to fix securely onto specific points under the car, typically here ;
There will be a cut out or indentation behind the front wheel and infront of the back wheel that will accept the head of the jack. When the head of the jack is located at the correct points, it should not move about whilst you are operating it and raising/lowering the car.
How do I do it safely then ?
For the purpose of this exercise we will assume that you are changing a wheel on your car.If you are performing something else under your car, just stick to the stuff relevant to chocking the wheels, raising the car and securing it.
Step 1.
MOST IMORTANT – find a flat and solid surface to jack up your car.
Don’t jack up any car when it is not on level ground or has an uneven surface.This is just asking for trouble and you could end up in hospital or worse.
Step 2.
Make sure that the handbrake is fully on and the car is in gear.Step 3.
Secure the wheel on the opposite corner to the one you are removing, example if you are changing the wheel on the front passenger side (nearside), then you should secure the rear drivers side (offside) wheel. The wheel should be ‘chocked’ so as to help prevent the car from rolling when we lift it with the jack.I have chocked wheels with house bricks or pieces of wood in the past, but the most secure and safe method I found was proper ‘wheel chocks’ (see picture below).
They were very inexpensive to buy and are far safer than using anything else and the can potentially be a life saver so why cut corners ;
Step 4.
Put the jack into its jacking position and take the weight if the car slightly. DO NOT LIFT THE WHEEL OFF THE FLOOR. If you are using the manufacturers jack then it will be easy to locate the correct jacking position. If you are using a trolley, bottle or scissor jack you will need to find a strong and secure place under the car to position it.
Example of secure position for jacking when using trolley jack
Here are a couple more examples of jacking points, your owners manual or Haynes Manual may help you identify safe jacking points also.
Step 5.
The reason for not lifting the wheel fully off the floor is so that we can loosen the wheel nuts slightly and with it on the ground the wheel won’t spin around. If you were to jack up the car fully and then try and loosen the wheel nuts, the wheel will most likely just keep turning around.So with the weight of the car on the jack, take your wheel bolt spanner (or wheel brace/spider as shown below) and loosen off all the bolts very slightly.
Step 6.
Now raise the car slowly with the jack until the tyre is off the floor.Step 7.
At this point you can now fully remove all of the wheel bolts and put the safely to one side. Now you can remove the wheel by just lifting it off the car, mind your back as large wheels/tyres can be heavy. Place the removed wheel under the car as a back-up to the jack.NOTE – if the wheel is stiff and does not want to come off, put one hand on the top (6 o’clock) and one at the bottom ( 12 o’clock) and try to rock it loose. It should not require too much force/effort to get the wheel loose but take care not to rock the car off its jack.
Step 8.
Now you can fit your replacement wheel, making sure that the bolt holes on the wheel are lined up with the holes on the car wheel hub.Line up the holes and refit the bolts you removed earlier.
With the car jacked up, tighten each bolt as much as you can until the wheel starts to turn. Now to ensure that the wheel goes on straight, make sure that when you tighten the bolts, they are tightened up as follows ;
4 stud (bolt) wheels
5 stud (bolt) wheels
Step 9.
Lower the car to the floor with the jack and remove it. Now perform the final tightening of the wheel bolts using the same sequence as shown above.Step 10.
Remove all tools and equipment to you have used and store them away safely.
FINISHEDIf you changed a wheel because of a flat tyre/puncture then go and get it repaired or replaced straight away.
Recommendations :
If you don’t have any axle stands to use when working under your car, you will need to put something else under the car to either protect you or to stop the car from hitting the ground if the jack fails.What I normally do if I have to take a wheel off is to put it under the car when I have removed it. I usually place it in its side under the lowest part of the car or under the side sills, so that if the car does fall (say with you under it), the wheel will at least offer some protection from you getting totally crushed.
ALSO,
Get yourself a good wheel brace, don’t rely on the spanner supplied with the vehicle.I have managed to snap a few of these as they are not very well made.
Consider a trolley jack, they are easy to use.
No bending down near the car to lift it.
source- http://www.carbasics.co.uk/blog/how-to-jack-up-a-car-safely/