Washing

I've thrown mine into the dishwasher for years, and they still look good. I hand wash the rare things, but the basic dishes I just machine wash.

Sometimes I've found dishes with knife marks. My stainless steel knives don't make any marks, but soft steel or silver can make marks. To remove them, I've sometimes had to resort to No. 7 polish (from the auto supply store). The dishes looked new after polishing. I've used solvents on them, and nothing bad has happened.

Cooking

They claim to be oven-safe, but I'm always very careful with heating them. I think they might be ok in the microwave, I've used them in it before without any explosions, but your mileage may vary. I fill the coffee pot with hot tap water to pre-heat it before I put hot coffee into it. I've never crazed one, and I've never seen any with crazing, so they are probably pretty resistant.

 From: "D. Bryan Chaney" 
      I have microwaved mine so many times they glow, but nothing bad has
 happened, like: chipping, crazing, cracking...  I have a pretty
 industrial microwave too.  I microwave several pieces a couple times a
 day.
      I tried to heat some food in an electric oven once and broke a
 dinner plate.  It cracked down the exact center like it was cut with a
 laser.

Breakage

 It takes a pretty good fall to break them. There isn't a whole lot you can do if you do break a dish. However...
You can make them into things:
Smash up broken dishes and use them in mosaic. Grout them onto flower pots.
Turn cracked teapots, coffeepots etc into lamps.
Use chipped dishes as your every-day dishes, and save the good ones for special occasions.

Lead?

 From: "D. Bryan Chaney" 
 I bought a lead test and tried it on a broken bread plate.  It passed.  
 Lead was undectable--I used the same swab on a door and it turned red.  
  The Starburst passed.  The door failed.

Collecting

Buy the rare stuff first, if you plan on collecting. You will find piles of common stuff at good prices if you go for the rare things first.
Don't buy damaged stuff. You won't enjoy them, you can't sell them, and you can always make your own.
Don't pay high prices for common stuff. Shop around. I saw a dealer selling teacups for $12. Your reaction to prices like these should be: HAHAHAHHAHAHAHAA!
Pay high prices for really rare stuff. If you see something really rare, and it is priced a little high, buy it anyway. You will regret things you let go later. Don't pay insane prices, but expect to pay the full retail price.

Price Guides

Just check on eBay.

Damage

 Here are my terms for pottery damage, and my rating scale.

0 is perfect. I'd keep my slobby pals away from this good stuff.
1 you probably would accept from the factory.
Stuff with these problems is usually sold 'AS IS':
2 might be sold as a second from the factory, but is close enough to perfect for your china cabinet unless you are extra fussy.
3 is good enough for every day use, to save wear on your better stuff.
4 is a bit gimpy, and you'd avoid using it if you had friends over.
5 might go in the trash.
6 is usually for smashing up into mosaic.

0 Wire marks
Not damage, just marks from support wires from the firing process.
1 Pinhole
Small dot of ceramic was never glazed over.
2-3 Bare spot
Area of ceramic was never glazed over, might be a factory second.
2 Nick
A small area of glaze has been knocked off up to, but not through, the ceramic body.
3 Scrape
A larger area of glaze has been rubbed off.
4 Chip
A small piece of glaze and ceramic has been knocked off.
1-2 Blotch
An area of the glaze has a different color or density of speckle.
1-3 Misdecaled
A decal was broken or placed badly.
2-3 Stain
A stain that does not seem to be removable. This happens sometimes if the piece is crazed.
1 unstamped
They forgot to stamp the manufacture's lable on it. This bugs people trying to sell more than it bugs collectors.
0-1 Knife-mark
The surface of the glaze has marks on it that can be buffed off.
1-3 Scratch
The surface of the glaze has a groove in it.
2-4 Scuff
The surface of the glaze has a pattern of multiple grooves in it.
1-4 Crazed
The glaze has a crackle pattern on it. Some patterns suffer from this problem much more than others. It hurts the value less when it is a common problem.
3-4 Dead
The pottery does not ring when tapped, possibly indicating an invisible crack.
4-5 Hairline-crack
The pottery has a crack on one side that doesn't penetrate to the other, and that does not seem to do structural damage or leak.
5 Crack
The pottery has a crack right through it, but is not broken.
6 Break
The pottery came apart and was glued back together.
2-3 Second
A slightly defective piece sold at a discount by the factory.
4-5 Third
A really defective piece, probably salvaged.
Knock-off
A piece that resembles a well-known piece
Copy
A piece that very closely resembles a well-known piece
Forgery
A piece that was sold misrepresented as something else
Marriage
Usually the wrong lid on a piece.

Dealing through the mail

 Don't accept being cheated by mail. It might cost a little more, and take more effort, but you should take legal action if you need to. There are steps you can take to avoid flim-flam.