Brick walls can be hard to break! Sometimes it takes researching everyone in a cluster around your ancestors: friends/family, associates, and neighbours. When done successfully this method of research provides a more personal touch to findings.
Land and property records, while often tedious to locate and understand can hold a surprising amount of information on our ancestors and help establish a timeline of events.
Process of Elimination
A more time-consuming but extremely effective method is the process of elimination. When lots of potential matches are found, but you can't determine what one is correct. I would build a tree for each and everyone to eliminate or confirm their link.
Probates and Inqusitions
Again, often tedious to understand and locate, probates and inquisitions provide a lot of information both on the individual concerned, but also generally their friends and family.
Location Based Research
Sometimes the way to the answer is less direct. Instead, a focus on the village or town your ancestors resided in will yield better results. This is best suited when you already have narrowed the family down to a specific area.
These documents provide an interesting insight into the individual's mindset, although are more often than not concern our ancestors probably want to be forgotten.