Other than letting the little ones walk and a little luck, the number 1 thing is you have to hunt an area that is known for producing big bucks and an area that is practicing good management! If you are hunting for a buck that is big for your area, letting the smaller ones walk will be about all you need to do. If you are talking about true B&C trophy or close to it, you may have to be willing to change areas or even regions. In my area of East Texas, management is almost non-existant and we have a poor buck-doe ratio! A 120" buck is possible, but if you are looking for something much bigger, you'll have plenty of tags left after the season! So, for me, it would take travel and $$$ to get anything better!
Hopefully, in your situation, there is huntable land nearby, that is capable of producing big deer AND is being managed properly! Good luck!