Recently a guy that I work with had been growing his beard out for about 6 months, it was long. We went out in the middle of the day (some photographers will refer to this as devil light) to see if we couldn't get a decent picture before he chopped it all off.
Here is the original exposure:
I tried to underexpose, I really did but the sun was just too bright and the result was a somewhat half washed out portrait.
I'm keeping this brief and so I'll get down to the nitty-gritty. If you don't have photoshop knowledge then I recommend picking up Adobe Lightroom, it's great for quick non-destructive edits. (I get paid $0 from Adobe, they just make great products so it's easy to recommend.)
Adjust your white and black levels first, this will give the photo some more punch. Try and use the 'recover' slider, it is great for getting rid of some of the harsh light in super contrasty photos like this.
Next, start using the burn and dodge tools, get the important areas, the eyes, lips, mouth. Don't over-do it though, I usually only burn and dodge at 5% opacity. Anymore and it's easy to ruin your photo.
Then, use the high-pass filter, probably somewhere between 100-200, you can always decrease the opacity of the layer later on if you want, then after applying the high-pass use the blending options to get the right feel for your photo.
Lastly, bring out the eyes a bit, they are the window to the soul and the most important part of a portrait, use the a screen blend option and make an inverted masking layer, color the areas that you want to be lighter with the black brush.
And voila! You can get some great results to this, there are some additional things you can do as well to bring out some details, have fun and play around with this stuff. Note that there is no end-all technique to creating portraits, the lighting of each photo is unique and must be treated as such.
Here is the end result of mine:
