The hardest part is definitely to get people to listen to instructions from the raid leader. I'll take the most recent dragon raid I was at as an example. While running there after assembling the needed amount of players, the raid leader explained the rules of engagement on the way. And other participants commented on in other channels that he knew what he was talking about. One of the rules was to stay very very close to the dragon, as it would otherwise be able to 'single you out' if you ran a certain distance away from it, and would breathe fire on you, killing you and the people within a small radius of you. We get to the dragon and people seemed to forget quickly about that rule, especially 'support classes' who apparently preferred to heal from a distance, thus getting killed first. [DAOC, M, 31]

Sometimes people just get too caught up in the fight to remember specific timing or a specific plan, after more experience people are able to strategize better because the novelty will have worn off. A perfect example of both these cases is one particular raid in EverQuest: Online Adventures my guild teamed up with another guild to take down one of the dragons. Pre-raid instructions were given on the strategy we'd use and tells to look for to avoid AOE's and other attacks. We had about 40 people show up to take down a relatively easy high end mob but because of people not listening and dieing our healers would need to waste mana and time healing/raising these people who didn't listen. After several tries we finally took him down and even with the problems it was still a blast. [EQOA, M, 22]

The hardest part of a raid is getting everyone to cooperate and work together, especially if it isn't a guild raid. One raid that I remember is a raid of The Deep in EverQuest. We had come to this invisible bridge, with a fake visible one next to it. A few people ran ahead and just ran across the fake bridge and feel off before the raid leader explained what we needed to do. After everyone started following the beast lord pets across the invisible bridge people did not follow correctly and fell off. It is mistakes like this that slow down the raid and make it less fun for all the people doing this correctly. [EQ, M, 16]