You've just bought a great adventure module at your local gaming store or the awesome RPGNow and though the adventure is great, how do you get the players there. The old standby 'you see a mysterious stranger in the tavern and he walks up to your table' shtick. When all else fails there is nothing wrong with that version especially if time is an issue. Just maybe switch it up a bit. The guy doesn't have to be mysterious, or a stranger or not have to walk up to the party. Could be a buddy they knew from mercenary school who gets tossed onto the party's table and as he is being drug away he screams for help.
How do you get the party to this awesome adventure you are dying to run? First of as a GM you should know what motivates your players. Wealth? Power? Purpose? Shits and giggles? Whatever it might be alter the adventure slightly to include the carrot that will have them chasing after your adventure. If your party wants to find a sword of power maybe put on in the adventure or at least in a rumor. If the party wants money, easy enough, you know what to do. Purpose you may need to alter the adventure more if your party plays a demon police and have made it their cause to purge this plane of existence of demonic presence then take the time to switch out a few critters, slip in a demon boss or at least some minions that are mucking up the works. For shits and giggles players just straight out have someone tell them "Hey there are monsters in that direction." And off they go, leaving half drank tankards and disgruntled bar wenches.
Be careful using canned modules. The main reason, the players may own them and know them better than you. This is something we've run into in our current campaign. One of the players used to run the canned module regularly when he GMed so when it came time for him to adventure through it as a player, he knew it better than the GM. If you run canned modules take the time to change a few things around. Swap some critters out. Or move it down the timeline say a few decades from when it was written. I always enjoy playing those 'what if' games. What would the Tomb of Horrors look like after thirty years of adventurers going through? It would be a lot different than written. This way the adventure stay fresh, but it still holds the mystique old adventure. "My god, what happened to the green face devil?"
GMs know your players. That's the easiest way to get them involved in an adventure. And enjoy the adventure. Just don't be lazy with you canned modules. A little work will go a long way.