Some ways that I can tell a DM is pretty much against the party and not leading a campaign:
1. None of the other players seem to be having fun.
2. Each encounter begins seeming beyond the total party level.
3. Combat drags on and on almost never ending and I am wondering if all the monsters can be dealt with.
4. More than the DMG percentage of encounters are deadly.
5. DM is overly secretive and or controlling with rolls or information.
Some things can be laid down purely to a fledgling DM that doesn't know how to adjust his game to the level of PC's and/or players, and when approached on the subject is willing to listen in the "AAR" or After Action Review. This is something I like to do at the end of a session to get feedback from players as to how they think the game went. If players want to find lot's of treasure and magic items and such, I'm fairly content to meet their needs in the name of having fun and being a "True Fantasy Hero."
I have played in games where we have been being killed off slowly one at a time and wondered amongst ourselves during the breaks if we wanted to venture down the next dark hallway or open a door for fear that the DM had some diabolical sinister way devised to kill off another PC and simply laid it off on us as not being able to find the weakness of a monster/demon/devil and exploit it to win/survive an encounter. Thats purely a load of smelly dung. If I were in a large room of bloody chains swinging from the ceiling, and unknown to me the creature that I am locked in mortal combat with is a Chain Kyton, yes my father forgot to tell me about them and most importantly, how to defeat/destroy one, I would probably die since I already know that running away would be futile as some other horror is lurking nearby waiting to rend the flesh from my low level body.
Each game should contain encounters that heroes can and do successfully survive, a little dented and dinged, scratched and cut for the most part, but all baddies dispatched with a flourish. A couple of dangerous encounters that may knock a PC down and out, but not kill. And the dreaded, way over your head and I want to see if your smart enough to just run away and live to fight another day. As a DM, I take no pleasure killing those PC's that look at each other and you hear the "Come on man, we can take him." I try to avoid killing them if after a round or so they really think they can do it, but should they decide not to heed the signs of the gods, I normally kill them very slowly in some horrible and sick fashion and then tell them, or sometimes show them the DMG and say "That was the encounter you were supposed to be smart enough to avoid. It's right here in the book, and the creature played no part in the overall adventure/campaign, he was just there to make things really really dangerous."
DM's don't cheat. They have power and control issues, but don't cheat. DM cheating is something that I have had some minor experience with, but can't really say for certain because I just stopped playing with their group. As a player, you should be able to quickly tell the difference between a DM making a mistake, and seeming to always be making mistakes that sway favor or balance away from the party. As a DM, I prefer to and prefer that my DM make my Spot, Listen, Open Lock, Disable Device and a couple of other checks, as outlined in the Core Books. If I have to roll a die as a player, then I know something is up, if the DM tells me I hear something, then I heard it. If I miss a die roll, then I know there was something to hear, but didn't, Follow me ? If there is something about the DM that makes me feel uncomfortable with the way they are conducting their game, I may be being cheated. Follow me again ?
At 39, D&D is my outlet. No psychological issues that I am going to publicly declare, hehehehe, but when I play or DM, I get to be a hero. Xaels Greyshadow, master rogue, shadow of the night, thief of fair maidens hearts and killer of all that is evil and foul. As DM, I get to tell a story that players interact with. I get to use my imagination. I can add, subtract, multiply or divide any published campaign or adventure. It's no fun when the DM is constantly going on about what's next to challenge me, insert word "Kill" there. That's overtly a DM telling his party he is out to make things as difficult for them as possible and if they survive it will be a miracle. There is nothing better than a few hours of fun that I actually enjoy comming home and recanting my tales to my kids and girlfriend while they look at me googly eyed and say I'm crazy.