The tutorial I used is taken from http://tutorialblog.org/photoshop-tutorial-getting-that-great-x-pro-lomo-look/
Step One: Open the image, if you've previously worked on the picture make sure all the layers are flattened before continuing.
Step Two: The first thing we’re going to do is widen up the lens angle a little bit. Go to Filter > Distort >Lens Correction and drag the top slider (Remove Distortion) a tiny bit to the left. Don’t overdo it, but make it look like the lens warps out a little
Step Three: . Next, copy the image layer and hit Q to enter quickmask mode. Press D to make sure you’re painting in black, and B to select the brush tool. Select a nice, big, fuzzy brush, at full opacity and a low flow, paint in most of the image. Stay away from the corners.
Step Four: When you have kind of a big, red, fuzzy circle, press Q again to exit quickmask mode. Go to Select > Modify > Feather and enter 10 to 20 into the box. Press OK.
Step Five: . Use Filter > Blur > Lens Blur to give it just a little bit of low-quality blur. I used a triangle shape with Radius: 8, Blade Curvature: 67, and everything else at 0. Press OK.
Step Six: Press Q again, B for your big, fuzzy, low-flow brush, and paint in almost all the image again, staying away from the corners like before. Then press Q again and use Select > Modify > Feather at the same number as before. Create a Curves Adjustment Layer and drag that line down in a couple places to make the very corners of the image really
Step Seven: Create another Curves Adjustment Layer. Give your image a tiny little “S curve” to start out with, then go to the Red Channel. Drag the top right point over to the left a little less than one quarter of the way. Then move the bottom left point over to the right a little more than a quarter of the way.
Step Eight: Open the Green Channel. Create a dot around the top right quarter of the line and drag it up and to the left just a little bit. Go to the Blue Channel and make a dot in the same place, but drag this one down and to the right a little bit. (see screenshot).
Step Nine: . Press Q again, B for your big, soft, fuzzy, low flow brush, and this time just draw a big circle almost the whole height of your image, not quite centered, not quite perfect, in fact the less perfect the better it will look.
Step Ten: When you’re done, press Q to exit quickmask, Select > Modify >Feather again for a little more than your last number, and then create a Curves Adjustment Layer. Make a dot in the middle of the line and drag it down about 1/4 the way toward the bottom right of the square.