We will use a rather plain photograph that will make the end result even more noticeable.

Next we will start creating a series of layers that will give us the lomo effect. First layer we will need is an Adjustment layer and more specifically a Curves one. Just click on layers and on the drop down menu follow Adjustment->Curves as shown below.

The Curves layer will bring forward the Curves dialogue window, where you can play around with the colors axes. We will work with the input and the output of the RGB, the Green and the Blue colors. This will adjust the density of the chosen colors and will start our picture resembling a lomo effect.

On the RGB and Green we will increase the input and reduce the output and we will do the opposite with the Blue. The images below will give you a good idea of how you want to adjust the axes of the Curves layer.

You can already start noticing the retro-ish impact on your photograph. We will continue our tutorial with another layer. This time we will use a Gradient map layer. The way to do this is the same, Layers and Gradient Map, shown below for your convenience.

Once done so, the Gradient Map dialogue box will be brought forward, which is preset in Black and White and which is exactly how we want it to be. Next click on the layers tab and set the lighting mood to Overlay, thats the first drop down menu on top and then lower the opacity, do this to your liking. We will use a 40% opacity in this case but this is more of a rule of thumb case.

If you want to perfect your lomo photo you can give it a tunnel vision effect. For this we will need another layer. This layer needs to have Black as a foreground color which we will then feather to give us the tunnel effect.
To do this create a new layer and having chosen Black then choose Edit and Fill from your top navigation bar.
This will bring up the Fill dialogue box. Hit OK.

Next choose your Rectangular Marquee Tool and draw a Rectangle in your black layer, not too large, it has to big a bit larger than the main object of your picture.

Once you are done drawing your rectangle, reach for your Feather tool. You will find that if you click: Edit->Modify->Feather. This will bring up the Feather tool dialogue box. Next we will set the Radius, this has to be related to the size of your picture, play around with the radius to see what works best for you. We used a radius of 50 pixels. This will black-out the peripheral area of the picture and leave the main object into focus with a black halo effect, which will be the tunnel vision. If this sounds too complex, dont worry, it is not. Just experiment with the radius and once you get it right you will know it.

Hit OK. If the picture comes up too blackened, simply reduce the Opacity a bit.
The result is an astonishing lomo effect!

With laso tool selected start drawing the outline of the teeth. Use the shift key to correct the parts of the teeth you have missed and expand the selection. When your selection is ready zoom out and hit ctrl+alt+D, this will open the Feather Selection dialogue box, and choose to feather this by 1 pixel. This way you will avoid the rough edges on your selection.

In order to whiten the teeth select the Curves Adjustment Layer, on the diagram that will open put your pointer in the middle and the input about 135 and the output to 132. So using the laso, then feathering the selection and using the curves adjustment layer is a quick way to whiten the teeth on the models of your images.

Also, check out how to make digital cosmetic surgery. Remember that beauty is in the eye of the beholder!