Ever heard of "Moneyball"? It was a book written by Michael Lewis with Billy Beane (GM of the Oakland A's). In the book, Lewis details Beane's approach to running a team by targeting areas that other teams ignore. Beane would consolidate his limited resources (by baseball standards) into these areas. At the time of the book, this focus was players who got on base a lot (especially via the walk), because teams were not valuing those skills as much as others.
If you asked any old timey scout, journalist, or baseball exec about "Moneyball", they would tell you it's that book written by Billy Beane about drawing walks, hitting homers, and ignoring defense. Well that's not true at all; one might assume - rather correctly - that these people didn't even read the book and were just drawing their own conclusions based on limited observation and hearsay.
So now you are asking "uhm, sloth, what does this have to with HP and me?". There is a post on the new player forum right now by a player who posts the same topic every couple of months. He continues to insist that only front line melee types need HP, and that divines, arcanes, and other "non-melee" types can ignore HP and dump con. He will also tell you that the regular forumites insist that every character max CON, take every HP enhancement available, and put all their efforts into being a big bag of HP, despite the fact that no one has ever posted that.
You see, this player is preaching against his own assumptions, and he is wrong.
When you see someone talk about not dumping CON, that does not mean max it out. No one expects a non-melee toon to take toughness III and IV enhancements, and certainly no one expects a first life toon or new player to have green steel HP items.
You will see lots of responses to this post (I HOPE!!!) detailing different visions of what your HP should look like. Allow me to offer you one such vision*:
1. Try to put at least 6 build points into CON at character creation. Trust me, you can spare them. You can put more if you are a melee or if you just want to. Some builds are build point starved. I had first life TWF paladin that started with a 12 con (4 build points). Like I said, try for 6.
2. Take the toughness feat. It's not just a total of 22 hp at level 20; it also opens up the class and racial toughness enhancements. Depending on your build, that could be anywhere from 20 - 80 hp.
3. Wear a level appropriate false life item. They are easy to find. You don't have to buy one on the auction house, they drop frequently.
4. Wear a level appropriate +x CON item. See #3 above.
5. Wear a level appropriate fortification item. This won't boost your HP, but it will help alleviate critical hits. If you've ever been wiped out in a circle of trolls or ogres, take a look at your fortification.
Finally, understand that your "role" will not protect you. It does not matter if you are not a front line player. Traps do not care if your are not a melee. Casters with cometfall and disintegrate do not discriminate. Devils can teleport past the front line and right to you.
I hope this post encourages everyone to read "Moneyball" - I mean, take their HP more seriously. There can be a fine line between running away screaming and healing, and asking who picked up your stone. Don't be on the wrong side of the line.
* - This is, just like my opinion man. Other opinions will vary, see posts for details.