My party list goes Me, My companions, Shielded troops, Calvary with Shields then Archers and Unshielded troops at the bottom. Usually it's all my companions, then shielded troops that join me in the Bandit camp, but every now and then an unshielded troop or archer sneaks in. It definitely seems to work for any companions that aren't injured. They will always join you if they're at the top.
Also just as a side note, if you get married and keep your spouse in your party, your wife/husband never joins Tournaments but will join you for battles and bandit camp raids.