This issue pops up from time to time on private pilot, airplane single engine land practical tests. I have observed that for some reason, as yet undetermined, some applicants exhibit confusion about following explicit instructions from the control tower. After calling up with the correct position -- say, 8 miles southwest of the airport -- and being instructed to join a left downwind, several applicants have tried to "swing wide," fly well past a logical entry point and and join on a 45 degree angle as if joining the pattern at an uncontrolled field. This, of course, is contrary to ATC instructions, and frustrates the tower because they were counting on the aircraft to join the pattern at the designated point. In fact, they were basing their sequencing on that expectation and had to shuffle the whole pattern to accommodate the pilot's "creativity."
Since I've personally observed this a few times now (in two cases, resulting in a Notice of Disapproval) I'm wondering if this simply isn't being properly explained or taught by flight instructors. What's odd about it is that in all but one of the cases in which I was witness to this behavior, the applicant was based at the busy class D airport and was quite accustomed to tower instructions to join the pattern after returning back from the practice area. I wonder how it wouldn't have reared its head during the regular course of training.
As has been stated above, simply follow ATC instructions. If you're told to join on a left base, join on a left base. If they instruct you to join a 5 mile file, do that. Don't add any creative touches.
Larry mentioned that if the entry doesn't make sense, ask for something else. The most common reason for the tower-requested entry seeming to not make sense is the pilot's incorrect advisement of his or her location on the initial call-up. Suggestion would be to take a quick minute and be sure your location is correct before sharing it with the tower. Goes a long way towards avoiding problems.