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.
Of course, a defendant in a criminal case would want jurors that are likely to be sympathetic to him. Therefore, good defense lawyers try to pick such jurors for the jury.
The jurors may symapthize with a defendant because of race. Having jurors who are of the same race as the defendant (particularly if the defendant is not white) is seen as an important thing. Some jury selection experts believe that defense attorneys should choose people who do not look like they are too conventional and attached to "establishment" ideas. For example, they would prefer to get a many with long hair on the jury over a man who is wearing a suit and tie. They also believe that people in more "caring" occupations are more likely to have attitudes that would favor the defendant. It is also believed that poorer jurors would be more sympathetic than richer jurors.
Basically, a defense lawyer is looking to get jurors who are likely to feel sympathy for their defendant and for defendants in general.