I'm trying to avoid the cliche "You are all sitting in a tavern" beginning in my next adventure. Say for instance, the setting of the campaign involves the characters as members of an army. They start out as new recruits and progress from there however their little hearts desire. If I let them know and ask them to incorporate a reason for joining the army as part of their character back story, do you think that would be too much railroading?
Would starting earlier and giving them highly suggested "choice" be a better option?

    I've run adventures before where the characters started as slaves/gladiators/down-trodden peasants, but all those scenarios made more sense because they were somehow forced into the situation. This time, the setting wouldn't really work out unless the PCs are acting voluntarily.

    I realize that after the players start in on it, "The best-laid schemes o' mice an' men. Gang aft agley". So essentially, my question boils down to how much direction do you think is acceptable before any actual playing begins?