Discussions about railroading seem to go on and on. Not content with defining a railroad as an adventure without choices, we worry that we might be manipulating the players too much, engineering our own agendas under the guise of playing a sandbox campaign. After all, just because the players can't see the wires pulling their actions does not mean the wires aren't there.
Ah, paranoia. I'd say you're safe if you're worried about your power to influence your players in a certain direction, but I know that's not going to be enough for those who want clearly defined boundaries for how or when they're allowed to finesse the players in their campaign.
With this in mind, allow me to make use of a moment of decision in a movie with which most of us are familiar - the moment when Morpheus offers Neo the red and blue pills. Even if you have never seen the film (I suppose that is possible) you must be genre savvy enough to know what the choice meant and how it played out.
The question is this: could Neo have taken the blue pill?
The easy answer is yes. True, the rest of the film relied upon his taking the red pill, but since role-playing isn't a movie and doesn't need a shooting schedule, what might have happened to Neo doesn't actually matter. If Neo had been a player, it appears from the film that Morpheus was completely sincere in the blue pill being an option.
Still, the answer yes is meaningless until we decide what effects the blue pill would have caused. It probably wasn't this. From Morpheus dialogue, all we truly know is this: "The story ends, you wake up in your bed and believe whatever you want to believe." A good discussion about that consequence can be read on this page. Quote:
"Does this mean that the blue pill acts as a selective amnesiac? A program to make Neo feel as though he dreamed the meeting, similar to his experience of having a bug implanted by the Agents? Would it include something that makes him no longer of interest to the Agents? Since, technically, all that Neo has to do, if he refuses Morpheus' offer, is get up and leave the room, why have a blue pill at all?"
Within a campaign, the red pill is the most obvious or the most desirable choice. It may be the choice that the DM clearly wants or the choice that seems to bring the most treasure or promise of other reward. The blue pill, conversely, becomes the lesser choice - the choice that appears to offer nothing of interest. The choice that only a party unwilling to adventure would take.
As a DM, deciding what it is the blue pill does is all important. The less valuable or meaningful the blue pill appears when presented, the greater the feeling the players will have of being railroaded. Having given them a truly distasteful looking blue pill, you have done the same as saying, "What would you like for dinner? Steak and crab with cubed red peppers? Or this lovely soybean paste mixed with overcooked beets?"
(there will always be those who choose the soybean paste - frikkin' vegans)
Sitting at your table four days before designing a red pill is challenging. So challenging, in fact, that very few DMs give a moment's thought to the blue pill. "No, of course you're not being railroaded. Yes, I have made this temple and dungeon, followed by a set of paths into the Tomb of Raschkammen the Dwarf's Head Collector, but if you're not interested in that, well . . . I guess you could hang around town awhile and see if there's some kind of trouble that emerges. A few tradesmen did rough up the tavern last night. Maybe you could go find them?"
The larger reality will quickly reveal that it isn't enough just to have a blue pill at the outset of the adventure. Every moment within the adventure must include a blue pill also! That means meaningful choice following meaningful choice, without let up, if you expect the players to feel that they're really in control of their destinies.
None of this says that the blue pill's appeal must be exactly equal with the red pill's appeal. It only means that the blue pill must at least suggest an alternative, productive course that could, later on,
provide adventures equal to the one we're on now. The blue pill should incorporate elements that the party could reasonably prefer to the elements offered by the red pill. Not everyone likes steak and crab. Perhaps lobster or pollo parmesan or even a spicy vegetarian chimichanga. In short, a reasonable alternative, taking advantage of the fact that even a hard-core adventuring party may not want steak every day.
Two final points, for the record. The first is that producing a blue pill equal to the red pill is a triumph. Any time the party is driven to conniption fits over being unable to decide between two perfect choices is a field day for me. Good times.
Secondly, I personally feel that a red pill and a blue pill are too limiting. There ought to also be an orange pill, a yellow pill, a purple pill, a green pill, a turquoise pill with pink spots, an oscillating brown-and-chanteuse pill, a mauve pill that spontaneously becomes black and vice-versa - and naturally a white pill that turns deathly grey whenever orcs approach.
In short, variety. Variety, variety, variety. Your fears of railroading your players stem from your failure to provide them with a suitable variety. Life is a smorgasbord, not a lunch special.