Andrei-

The only rule I can think of about sentences of this type is that the prepositional phrases that answer 'where', 'with whom', and 'about what' should be after the verb. The 'when' phrase may even go at the beginning of the sentence. Ex. "At 7:30 the game starts in Athens," or "the game starts at 7:30 in Athens," or "the game starts in Athens at 7:30." Being able to shift the positions of the prepositional phrases allows you emphasize the more important part of the sentence as far as the conversation is concerned. If you're talking about WHEN something will happen, place the 'at 7:30' earlier in the sentence. If you're talking about WHERE something will happen, put the 'in Athens' earlier, but it should almost always come after the verb. The same is true for the first and third sentences--if Dr. Rogert is most important, put him in the sentence as early as possible (but not before the verb). "I have an appointment with Dr. Rogert at 3 p.m."

The necessity of emphasis becomes more apparent when you have a lot of prepositional phrases in a sentence like this: I have an appointment with Dr. Rogert in Athens about my kidneys at 7:30 pm.

Hey guys, I am exhausted, and I find some of these posts really confusing: if Dr. Rogert is most important, put him in the sentence as early as possible (but not before the verb). "I have an appointment with Dr. Rogert at 3 p.m." So far so good! but why should people the time of the appointments with Dr Rogert and have it at 7.30. Why would people want to do that? Would that mean that Dr Rogert is still the most important thing? Could someone explain the logic in it ? Frankly, I don't quite get it.