Not trying to be flippant, but the first places to start are always the same... Learn the rules well. Teach them well. Then play the game to learn the mechanisms, not to win. Find players that do same also. Then once you've got the game down, play to win. You'll know how long it takes you to actually play the game. If it is still too long, then you'll be in a position to make adjustments.
First, I want to say that the game does not feel like it drags, game length feels alright. However, if you want to shorten the game I believe there is an easy way to do this. The Oil Baron's train is the timing mechanism for the game. At the beginning of each turn a Special Action Card is drawn. This card tells you how far the Baron's train moves. For a shorter game simply add 1 to the number shown on the card. I have never tried this, and it might make the game too short. Maybe it would be better to add 1 every time a 1 distance (the distance ranges from 1 to 3) is drawn instead. Good luck!