Hold out the horrid matting of hair and spray the heck out of it with a spray-on detangler or a moisturizing conditioner. Don't be shy, this clump of hair's about to make you work to get it out, so make sure you get it good and saturated.
Work the conditioner (or detangler) in with your fingers by squeezing it into the matted clump, but be careful and don't rub! The last thing you want to do is make the matting worse, and that's what you'll get if you try to rub the conditioner in.
Find a comfy spot and take a seat, depending on what shape your hair is in, you could be working at it for a while. Start working on the matted hair using your wide-tooth comb, beginning at the ends. It's probably going to hurt, but you'll need to work your way toward your scalp one centimeter at a time, loosening the hair as best you can as you do so.
Grab a small pair of scissors if you run across a particularly vicious matting of hair. Don't worry or go into a panic, the goal's to comb it out -- not cut it off. What you will need to do to in order to make it easier to comb through is use those scissors to take a snip or two at the thickest part of the clump. Give it another shot with the wide tooth comb after making the cut. Sure, you'll have cut some of your hair out, but it's better than having to cut the whole clump out.
Switch your wide tooth comb for your smaller fine tooth one (no, this one won't feel any better). Again start at the ends of your hair, which are probably a little easier to work with, and comb your way through the knots and mats that you've loosened up with the wide-tooth comb. Keep adding more conditioner or detangler as needed to keep the areas of gnarled hair softened until you're completely free of those tangles, clumps, bumps and knots.
Work out your matted knots while your hair is wet.
If you must snip some of your hair to work out bad matted clumps, you may notice some thinning in those sections of your hair once all the clumps are out.
In severe cases, it may not be possible to comb out matted hair. In those cases, your only option may be to decide on making a change; pick a cute short hairstyle and cut your hair.