There really is no surefire guaranteed method for sustained success, not the way the system is now, as we can see in the fact that no team has been able to repeat since the 2000 Yankees.
Avoiding any free agent deals longer than 3 years sounds like a great idea but it's pretty hard to get any top-line players on such deals. It will get you players like Cherington signed in 2013. It worked for one year, not so much after that.