I was playing Traveler with a GM I had never played with, who I will call "Bill." Bill told us that the ship was damaged, and the goal was to reach an escape pod and abandon ship. I was assigned a character that was normally played by a person, I forget her real name, I will call her "Jenny."
We played through the scenario, had a few combats, and then I told Bill that I wanted to go to the control room, and save the ship. Bill said, "Jenny wouldn't do that with her character." Bill then told me I must proceed, as per HIS PLAN, to the escape pod and abandon ship. Perhaps you can imagine how frustrating this experience was for me, it was a classic GM move called railroading." NO ONE likes to be railroaded. DON'T DO IT!!!
The opposite of railroading is allowing the players to do what they want, even if it derails your plans. For some DMs, it's hard to allow players that kind of control, but trust me when I say, what the players do, where they go, and what goals they attempt to achieve should be theirs to decide. You can offer guidance, in the form of adventures for them to complete, but if the players chose NOT to complete a certain adventure, then DO NOT FORCE IT.
You can ALWAYS build the railroad, put the train on the tracks, even give away free tickets to your players, but you cannot FORCE your players to get on board and ride to the destination you have pre-planned.
One technique my brother Stolph uses, Just-in-Time Campaign Building, minimizes the temptation to railroad by not investing a lot of up front time in deciding how you think the story should play out.
It's too late to implement this idea when resentment has built up and your players no longer want to play. If this happens, approach your players, tell them you made a mistake, and promise to do better in the future.