I don't know how it is done elsewhere; but, in Georgia the process is well-defined and formal. People who register to vote simultaneously register for jury duty. Jurors are called from a rotating list, that list being blind to party affiliation or other possible indicators. There are few excuses that are acceptable for dismissal. On the first day of each trial week, jurors report to the "bull pen" at 0700 in the morning, and are assigned a sequential number as they are admitted to the waiting room. Jury selection gates a specified number of potential jurors into the selection room. Both legal teams can dismiss jurors for cause until twelve remain. Neither legal team can influence the selection of people into the selection room, and arrival time is typically random.
The process seems to fair.
It does seem that more senior people are called to duty than young people.