Perpendicular parking is made simple
by looking at your side mirror.

Toyota Echo

This picture to the left is the drivers side view of the side mirror, in the correct position to come into the center of the stall when parking a car to the right into a perpendicular parking stall.

Notice, you pay NO attention to what is in the mirror reflection (unless you see a hazard headed your direction from the mirror :)

Look at the red line in the picture under the mirror. This is where you see the mirror itself in relation to that first white line of the stall. It is just a little forward of the center of the stall.

It will also look like your hood is parallel with the further line of the stall. If you turn, as soon as you let (lightly) off your brake, you will end up pretty close in the center of the stall.

You may also notice you can't see the far line of the stall, the car frame blocks it. No problem, we aren't using that line as a reference!

Caravan minivan

Notice the mirror looks a little further ahead in a Dodge Caravan or in a Toyota Corolla.
I would guess its because the Echo is shorter than these vehicles.

Toyota Corolla

I also found I couldn't see the end of the hood as well in the Toyota Corolla, I was probably sitting lower and or the hood sloped down more.

I therefore found it easier to watch the line come parallel with door handle, rather than using the mirror.

Toyota Echo

Here is the same reference point only parking a car to the left side. Again, the red line shows where the mirror is in relation to the FIRST line of the parking stall.

You will notice the line may look farther ahead than in the first picture. that is just because you are looking at it from the drivers side, so its closer and looks like you are further ahead than to the right.

Caravan minivan