You said it before, lens flare, but an easy way to do it, is using the brush tool :p
Another way is, just select the part you want it to have some lights with the Lasso Tool and make a new layer, and change the Brightness/Contrast, you can sharpen the render a bit.

Like :



It's really up to you, how you want it to look like, i just gave you some simple tips really. The animation is just to show you what it will look like.
Here is the psd to what i did. http://www.2shared.com/photo/-Gl6CCUg/signature.html