Buy your wedges as a separate set, not as extra fairway irons.

The Snake Eyes line includes over 30 wedges of various designs, ranging from mid-priced  to very high-priced.  Here is the 600T Forged Snake Eyes, a thoroughly trendy and very high-quality design, with a wider sole beveled at the back, and slightly less bounce. The exotic black oxide finish will wear off for that Tour-quality "rusty but trusty" look. About $70 per club.

  
Golfsmith's 650PM wedges.  Forged from a raw billet, but the billet is made of a powdered mild carbon steel with some aluminum and copper added.  Advertised as having the softest feel and greatest density yet in a trouble wedge. It definitely has a distinct feel, but its more "crunchy/crispy" than "soft".  Available in 3 loft/bounce combinations, and two finishes, neither of which is as pretty as the picture suggests.  Pricey at around $70 per club.

I didn't like it when I first put in in my bag, but now it is my go-to club from inside 80 yards... I look for excuses to use it.

WEDGES
Price- An individual wedge of premium materials could run you more than $90, or around $75 with steel shafts.  Less exclusive materials will be less than half that, down to around $30. See quality

Set Makeup- There are fairway wedges and trouble wedges. Most players carry, as they should, a pitching wedge that is really a 10 iron... an extension of their fairway irons set. If your chosen set of irons offers an "attack" or "gap" wedge, you should carry that too.  ( Actually, what passes for a modern pitching wedge used to be called an "8-iron" , but that's another story) 

There's a difference between those set-extention fairway wedges and a trouble wedge, which is designed as a club to use for heavy lies. To appreciate this, take a good quality set-extension wedge and a good trouble wedge off into some long thick grass, like what you might find next to or behind a green. Hit a few shots with each.  You'll feel the difference, and you'll get more consistent hits with the purpose-designed wedge..

You should have a separate  wedge (or even a set of them) designed for heavy shots  and trouble shots. Definitely, you should carry at least a big-flange trouble ("sand") wedge.  A smaller flange heavy wedge is a good option if you don't carry the long irons.

Material- What kind of metal a wedge is made of is the most important spec in a wedge.  "Kind of metal" means not only the chemical composition, but also how the individual atoms of the various elements link together. It is not a trivial subject...see Metalurgy, and if you want a good wedge, look for billet-forged carbon steel.   Better metals cost more, of course. A really good wedge has "feel", meaning it transmits the vibrations of impact with the ball to your hands in a form your hands can interpret.  Of course this does nothing for the shot you are currently making, but over time, it improves your average shot.  That's why all good players insist on wedges with good feel.

Forged carbon steel steel wedges are by far the favorite on Tour, where feel is everything. Stainless steel wedges are adequate for the casual golfer who doesn't want to spend a bunch. Recently, there have been many innovative experiments with other materials. Forged wedges are still the best, but they are not cheap.

If you decide to pay the price for forged wedges, take the time to practice with them.  There is no point in buying great feel if you don't let it work its magic for you.

Head Shape- Despite many attempts over the past 500 years, no one has improved on the basic, classic wedge shape. Bounce, sole, and camber however, are still subject to considerable debate, and matching bounce to the intended use for each loft depends on how you play your trouble shots and what your favorite course is like.  

In fairway irons, its important that the lateral center of mass be about half-way out on the face, to center the sweet spot.  But wedges are swung so slowly that they don't have a sweet spot. In a wedge, it is more important to keep the weight low, so that the clubhead can force its way smoothly through the grass, sand, and mud, or whatever else you have gotten your golf ball into.

There are dozens of quality wedge lines, so there is a loft/bounce combination available that is right for you .

Length-  Standard length for a wedge is 36 inches for men, 35 inches for women.  We adjust from there based on your stature, posture at address, and the way you swing your wedges.

Face Angle-  Wedges start at 46 degrees loft and run through  65 degrees, with literally everything in between available. A trouble wedge is not intended to be a distance club, but still, be careful not to leave an overly large gap between the distance of your shortest fairway iron and your longest wedge. Also check the full-swing distance gap between your pitching wedge and your sand wedge. If either gap is more than about 15 yards, you should consider a gap wedge. We can also adjust this with shaft length, but at risk of affecting your accuracy.

Incidentally, if you use forged or soft-steel wedges (See Metallurgy and read about carbon-steel and 304 stainless)  you should have your wedge lofts checked and adjusted every couple of years.

Shafts-  A good, reasonably-priced steel shaft is all you ever need on a wedge. Softer flex works well for many people. If you prefer the "feel" of plastic shafts and don't mind the price, that's okay, but a serious golfer should never get a cheap composite shaft.