When being confirmed in the Catholic Church it is customary to choose a saint. What criteria should we use to choose this saint? Should one choose a saint they like? Would like to be like? Or one that has strengths where I have weakness? What guidance has the magisterium given for this process?
Your instincts are good. I found this answer here:
The custom of adopting a saint’s name at confirmation was done in order to adopt the saint as a special heavenly patron or to honor a saint to whom one had a special devotion. In short, the purpose was to give the confirmand the opportunity to develop his understanding of and reliance on the communion of saints.
In my own case I chose Joseph as my confirmation name because we had a neighbor that was a good Catholic role model named Joseph (he was our boy scout troop leader) and I also thought Mary's husband didn't get enough devotion.
Apparently some parishes no longer ask you to chose a confirmation name. I think that's sad. Misplaced liturgical "reform".