ok i am pretty tired now but im gonna do my best :P
This tutorial will show u how to make a small sized car
like this one


ok here we go
1.
find a picture of a car. a picture taken from the side would be the best for this effect. but will also work with perspective view pictures. but those are alittle harder to do
now here's a car i found.. searching for CAR SIDE on google :P


2.
select the round marquee tool and draw around the the front wheel, click ctrl+c on the keyboard and then ctrl+v
do the same steps for the rear wheel


3.
now click ur backround layer ( the layer that has the car in it )
now click ctrl+a on your keyboard, then ctrl+t and drag it in, so it looks something like this


4.
now place the 2 wheel layers onto the car.
then if it has some weird looking edges. just fix em with either the erase tool/blur tool or just normal brush tool



5.
The car picture you chose possibly has some lines on it. for either the doors or for the hood or just something else :P
select 2pixel wide and 2-3 pixel high with the rectangular marquee tool.


6.
now copy that, paste it and drag it alittle up.
then scale it up not to the sides. so u have something like this


7.
ok this i cannot really explain. you just have to do it yourself to see how it goes. ctr+t click the layer, then right click inside the selection, then click WARP and drag the the top axes to the other line thats above the wheel,



8.
just use the erase tool and blur tool to get it looking smooth.


9.
as you can see there's a few errors in here. like this one

just click ur brush tool, hold down alt, click somewhere near the error to get the right color.

then just paint over the parts that's messed up, remember to use the blur tool aswell if it does not come out quite right.

10.
zoom out and your car will be pretty much done.

11.
just select the parts of the image that you want.

Ctrl+C to copy it
Now create a new image. the size will be automaticly changed to the size of the selection you made
now press CTRL+V on the new image. save the image. and you're done.
here's my final result.

I would suggest using cars with spoilers, and not too much of a active background. just some simple background. like the one i chose.
hope you liked it. please post comments and you're own results if you tried