To answer the second question first a couple examples of gladiator ads have been found in Pompeii and they said the following.

Gladiator Show

"The gladiatorial troop hired by Aulus Seuthus Certus will fight in Pompeii on May 31.

There will also be a wild animal hunt. The awnings will be used."

(CIL IV #1189 from Tanzer, 78)

"At Puteoli on the ?th of December, fights. At Herculaneum for the Security of the Caesars and Livia Augusta. There will be awnings. Iole greets you." (Website. CIL IV.3.4 #9969)

"A hunt, and twenty pairs of gladiators belonging to Marcus Tullius will fight at Pompeii on November 4-7." (Website. CIL IV.3.4 #9979)

Now as to the first part we have some idea on the rules. The biggest study was done in 2006 on the bodies found in a gladiator cemetery in Turkey. What it discovered was that few gladiators had ever been hit in the back of the head, always to the front or the side implying a strong rule against hitting someone from behind.The second major surprise was that few of them had repeated wounds like soldiers do. It appears that there was a code of honour with gladiators fight bravely and we'll but do not wound or kill unless you had to. The only other rule that I can find strong evidence for is if you fell over accidentally it was considered in much the same way as a knockdown in boxing you were allowed to pick up your weapon and start the fight again. If you fell deliberately the fight was over. In fact one of the tombstones in Turkey appears to be a gladiator saying a bad call by the ref lead to his death saying.

“Here I lie victorious, Diodorus the wretched. After breaking my opponent Demetrius, I did not kill him immediately. But murderous Fate and the cunning treachery of the summa rudis killed me, and leaving the light I have gone to Hades. I lie in the land of the original inhabitants. A good friend buried me here because of his piety.”

Another thing to note was that to train a gladiator was expensive so most of the time a gladiator would not try to kill. Also as seen in the ads above it talks about troops of gladiators. These gladiators would know each other and would have trained together so they would not want to kill each other.

A distinction must be made between the gladiators and the various other entertainers of the arena. Most people seem to think there were only two kinds of entertainments, the circuses and the gladiatorial games. This is about as far from the truth as possible. Although gladiators and circus races were the most famous and celebrated of the arena's entertainments, they were far from the only ones, or even the most common. In fact, both gladiatorial games and circus races were extraordinarily expensive, and were usually reserved for extremely important occasions, funded either by the state or private individuals. The vast majority of all gladiatorial contests were also at small contests, usually only a pair or two, funded by a private individual, usually in honor of a dead relative and attended only by a few people.

Because of this misunderstanding it's very common for people to assume that the gladiatorial games were just the bloodbath that we're used to seeing on TV. There were certainly some bloody entertainments in the arena--Seneca deplores the midday entertainments, which were essentially to throw a dozen or so pairs of condemned criminals into the arena, each pair chained together and with one man carrying a sword and the other a shield, and have them fight it out--but gladiators were not usually one of these. Most of the bloodier entertainments were products of the later part of the Principate, particularly after Commodus and during the Third Century.

In reality, gladiators were not the oppressed livestock that they are portrayed as being in films like Spartacus and Gladiator. Gladiators were like rock stars. They were slaves mostly, true, but the concept of slavery was pretty damn different in Rome than the concept familiar to us. Roman slaves could own property, for one thing. And damn did gladiators own property. Most of the successful fighters owned at least one villa in the country, and sometimes they would also hold shares in their gladiatorial school. In addition, the gladiator's prize money was enormous. Even though it was usually split up after a fight between the gladiator, his trainer, and his owner, the amount that the fighter himself received was no small portion, and three or four fights would generally allow a gladiator to retire and set himself up comfortably for life. Another thing is that gladiators were immensely expensive. It wasn't just a case of handing some buffoon a sword and telling him to go out into the arena. Gladiators were trained intensively for years at a time, and their owners pampered even the less successful fighters to no end, in order to keep them in perfect condition.

One of the most important reasons for the high survival rate is that gladiators didn't go into the ring intending to kill each other. Nope. Like I said, gladiators were expensive, and it was in the interest of both owners, as well as the gladiatorial guild (to say nothing of the gladiators themselves) to keep them alive, particularly since they could build up celebrity status after only a couple of fights. I'm an anime nerd, so you'll have to bear with me on this one, but the analogy that I like to use is that of Japanese (or Korean for that matter) idols, if you're familiar with them. A production team wants to advertise their idols aggressively but it doesn't want to exhaust them or waste them, since they're so damn expensive. Maybe a better example is NFL players. Those guys cost a lot of money and they gain a lot of fame. There's absolutely no point in having them actually kill each other, although they're perfectly capable of doing so in a game. Same thing

Another thing is that during a gladiator's entire career it was extremely rare for him to be engaged in more than four, maybe five (if he was a lousy fighter) fights. That's right. And the chances of getting hurt in one fight, or of actually killing or being killed, were extremely low. This is again because of the enormous expense involved in training and producing a gladiator, as well as the fact that during their matches, even though they rarely tried to kill each other, they expended a huge amount of energy to keep the crowd pleased and to increase their fame. Being in a gladiatorial match was incredibly exhausting, and fighters needed a long period of recuperation, particularly since their owners wanted them as fresh as possible before their next match. Which meant maybe three matches a year, tops.

As for those advertisements, they're quite literally everywhere. If you take a trip to Pompeii you'll see advertisements for gladiators and schools (which served rather like teams or production companies do today) all over the place. However, a great deal of advertisement was by word of mouth, and we see examples of this at Pompeii in the graffiti. A great deal of the graffiti at Pompeii has some invocation to a gladiator, or declares the writer's support for a particular champion (most of the rest of the graffiti takes the form of curses, or messages to prostitutes).

So what were the rules? We don't really know. There's some archaeological evidence to suggest that blows to the back may have been prohibited, which was also true of boxing (although then again, in the ancient world there was no jumping about in boxing like there is today. The two fighters stood--or sometimes sat--opposite each other and traded blows without moving until one surrendered or fell over. Manliest of men). Foul play seems to have been discouraged, such as biting or gouging of the eyes, the way it was in the Greek pankration. Note that the retiarius, or net-man, generally won as soon as he tangled his opponent up, without actually having to finish him off. We have almost no depictions or indications that retiarii would kill their helpless opponents, so it seems that the referee would probably just call the match when one side was no longer able to fight. This usually meant that one fighter was disarmed (disarming your opponent seems to have been among the most common methods of winning a match) or that one fighter got knocked on his ass. Here's another thing. Since most gladiators wore armor that left a great deal of skin exposed wounds and deaths should've logically been much higher. So why weren't they? There are several theories for this, but it seems that disarming or knocking your opponent over (and then presumably pinning him or something) were the main tactics employed by a gladiator.