Having spent twenty years practicing law, I can tell you that jury selection is a rather esoteric and sophisticated process which is much more complicated than some might indicate. It is dangerous to trust such matters to anyone who is not an expert. A persons's occupation will often tell a great deal about the person; for instance a framing carpenter might be willing to overlook small mistakes whereas a cabinet maker will not miss a single detail. The carpenter makes a better juror for the prosecution; the cabinet maker for the defense. The above comment about "establishment" jurors only applies if the defendant himself is "establishment. If the defendant is a businessman charged with a white collar crime, a long haired juror is probably a serious mistake. If the defendant is a young person, quite often an older lady is preferable to a younger one, as she will tend to be more "grandmotherly." A young woman juror is anthema for a young woman defendant, as the potential for jealousy is there. A potential juror's religious preference might also be a factor. As far as race, there are specific limitations on using race as a qualification or disqualification for jury duty.
One is not likely to find a jury member who feels sympathy for "defendants in general." Such a juror would be disqualified almost immediately. As far as finding a sympathetic jury; that qualifies as a classic understatement. As noted before, it is a complicated procedure and, like predicting the weather, is not always accurate. It is best left to the experts.