Do most people just set the secondary toon to be on follow at all times?
yes

What do people use in order to make accepting quests easier as well as repairing/buying items?
check macros forum for sticky thread, there is macro which accepts trade/quest/res and something else by one keypress

for repairing use Automation addon, it does autorepair when you click vendor who can repair

didnt understand what you mean as buying items
anyways you have to switch between toons in order to buy items