Here is the original photo.
It's not bad, a bit underexposed, but nothing too hard to fix.
So here's what I did, step by step. (If you would like me to clarify any of the steps let me know in the comments and I'll add a screenshot of that step.)
1. Adjust the exposure. In Adjustments, click Exposure and adjust it so the photo looks like it's the right exposure. (The exposure is the amount that the light lets in when the photo is taken. If it's underexposed, that means there was not enough light let in and the photo will look dark, like this one.) I adjusted the exposure of this photo to +1.7.
2. Add a photo filter. In Adjustments, click Photo Filter. I used Warming Filter (81) at 10% density.
3. Adjust brightness and contrast. In Adjustments, click Brightness/Contrast. I adjusted the brightness to 5 and the contrast to 10.
4. Adjust vibrancy. In Adjustments, click Vibrance. I adjusted it to +10.
5. Copy the background layer.
6. Use the Dodge tool on the eyes to make them more lively. I used the Dodge tool with Range: Midtones and Exposure: 20%. Get the eyes nice and bright, then lower the layer fill (in the Layers panel) until the eyes look natural.
7. Create a new layer. Zoom in on the eyes. You are going to add something called catch lights, which are just the reflection by a light source in a person's eye. Adding them helps to make the eyes more lively. Choose a brush with 50% hardness and make it the size that the catch lights would be. (On this photo there were already very light catch lights, so I just used them to determine the brush size and then made them a bit more intense.) I used a 56 pixel brush size. Click the brush once on each catch light (if you're using a photo that already has them) or click once on each eye in roughly the same position (if you're using a photo that doesn't already have catch lights).
8. Set the blend mode of the layer to Overlay. Turn the layer opacity down until it looks natural. (I used 25%)
9. Create a new layer filled with 50% gray. (Do this by clicking Create a new layer in the Layers panel, then clicking Edit, then Fill. Set it to Use: 50% Gray, Blending Mode: Normal, Opacity 100%.)
10. Set the blend mode of the 50% gray layer to Overlay.
11. While on the 50% gray layer use the Dodge tool on the parts you want to brighten (such as the shine on the hair and the lips) and the Burn tool on the parts you want to darken. (There might not be any but if parts of the face are looking flat and not 3D like they would be in real life, you can darken the edges to make it look more 3D. For example, on this photo I used the burn tool just a little bit where the shadows around the nose were.) This is the Photoshop equivalent of using highlighter and bronzer with makeup to contour your face. Doing it on a 50% gray layer set to Overlay lets you add depth to the photo with a lot of control.
And that's it. With this photo you really only need to adjust the exposure, if you're a Photoshop beginner, to make it look way better. The other steps are all optional and more advanced. I hope something from this tutorial is helpful for you. And definitely let me know if there are any parts of this tutorial that you would like me to explain further or expand upon. Like I said, this is my first Photoshop tutorial, so it's not perfect and I would love to improve it for you in any way possible.
Without further ado, here is the finished product.
