For this tutorial, I will be using Photoshop CS3.
Grayscale images will work best. If you want to work with a colored image, please follow this tutorial first.
Step 2: Most likely, Photoshop will recognize this image as grayscale. That's normal. However, we want to change that as we will be adding color to this image. Go up to image - mode - RGB color and you'll be set to use color. This will not affect your base image in any way.
Step 3: Create a new layer by going to layer - new - layer or hitting Shift+Cltrl+N on your keyboard. This layer should be above your base image. Fill it any neon color you'd like. I will be using #47b0d8. Set this layer to lighten and only fill it to 25%.
Step 4: Create another layer and fill it with another neon color. I will be using #8147d8. This time, I will lighten the image at 50%. Feel free to use what you think looks best.
Step 5: Create another layer. Using the polygon lasso tool (L), select a part of the image. You can do it vertically, horizontally, or diagonally. It does not have to be half of the image. I will make mine half and diagonally.
Step 6: Fill this selected section with yet another neon color. I will be using #e2fd2d. Next, go up to select - inverse or hit Shift+Ctrl+I on your keyboard. This will select the remaining section of your image. Fill this with a different color. I will be using #fd2d76.
Step 7: Deselect by going to select - deselect or hitting Ctrl+D on your keyboard. (You can also just right click and hit "deselect.") Set this half/half layer to multiply 57% or whatever you think looks best for your image.
Step 8: Now we are going to make the base image look sharper. We don't want the colored layers to overpower the image itself. On your layers box (often on the right hand side of Photoshop) click on your background image. Go up to layer - duplicate layer and make sure this duplicate is on top of every layer for now. Go to filter - sharpen more to make the image look sharper than usual. You also want to set this duplicate image to linear burn 10%.
Step 9: Go back to your half/half layer and skew it so the layers underneath are exposed. Go up to edit - transform - skew and turn the half/half image however you'd like to. You can do dramatic or subtle angles.
Step 10: Next you can add some other geometric shapes. I will add circles to the bottom left corner of the image. Using the elliptical marquee tool (M) which is just a rounded select tool, I will make circles. Make sure your setting are set on "add to selection" like so: that way you can create all the circles at once. After that, fill them with another color and set them to color burn 85%. I will be using #f42254. Next, go back up to edit - transform - wrap and alter the circles so they look distorted.
Step 11: To give the circles a little bit of "pop," you can add noise to them by going to filter - noise - add noise. I set mine to 7% but you can alter them however you'd like.
Completed: That's all I did. You can go as far as you'd like. The possibilities and options are endless!