To find a person, you have to locate that person in space and time. Genealogists spend a lot of their effort defining those spaces and those times that define the identities of their ancestors. But too many take the "Holes" approach to genealogy. If you haven't read the book by Louis Sachar, maybe you have seen the movie. In the movie a group of boys in a juvenile detention center are forced to dig holes in a dried up lake bed. Unknown to the characters and the audience, the boys are really looking for a buried treasure. Now if we ignore the need to define the space and time of our ancestors, we will end up like Stanley Yelnats digging endlessly, spending a lot of effort and sweat, but getting nothing for our efforts. The movie and the book turn out well in the end, but sometimes our efforts to find our ancestors don't turn out so well.
How do we keep from digging an endless series of holes in a dried up lake bed? I have a few suggestions. Place your ancestors in time and space. Where were you born? If you don't know, then that is the first step in your genealogical digging. I have said this before, but it bears mentioning over and again, your mother was there when you were born. Your grandmother was there when your father was born and so forth and so on. So how did your mother get to where you were born? By the way, the same rule does not hold true for your father, he may have been just about anywhere or even deceased when you were born. We spend a awful lot of time looking for male members of our families when it is the females that hold all the links to all the information.
Some our efforts will end right there. From time to time I do work with people who do not know their parents. You may have to use a whole different set of tools to find your parents and that is another day and another story. Let's assume you know where and when you were born. That is the location and the time period where you start to look for records about your parents. At this point, you learn everything you can about the history and geography of the place you were born. The more you know, the more likely you are to find records about your family. Hmm. While you are contemplating this problem, it might be a good idea to ask your relatives for information. They might know more than your think.
OK, you know who your parents were and you find out when and where they were born. Then you know where your father's mother and your mother's mother were at the time your parents were born. Now you need to find out some more about the history and geography of the area. Genealogical records are mostly located by geographic area. Now you are looking for records about your two grandmothers and you have a place and a time, the place your father was born and the time he was born and the place your mother was born and the time she was born. That is a good start. But, you say, I know all that and I am really looking for my great-great grandfather. If you are looking for your great-great grandfather, you are telling me that you don't know when or where he was born. Why is that? Because you skipped over the information and tried to get to your great-great-grandfather without ever knowing where or when he lived. If you know where and when one of his children, either male or female, were born, then you know one location and time for your great-great-grandmother and that is where you start to look.
I have focused on birth dates and places, but it is obvious that the idea is to locate at least one event in a particular location. The problem in finding your great-great-grandfather isn't really about him, it is about his children, at least one of whom survived to adulthood or you would not be here. There is one more rule, it may seem very cynical, but you have a much better chance of identifying the true mother of your ancestor than you do the true father. No matter how certain you may think you are, there is always a measure of uncertainty in any pedigree where the mothers are not positively identified. If you want to blindly ignore this principle, be my guest.
If you don't know where a relative was born or where he or she lived, then you are skipping a generation. Focus on the children. Find out as much as you can about the children. Where and when were they born? Where did they live? On and on and on. Focus on those events and places where you can positively identify the time period in which they lived and the place. Look for records at that time and in that place. Instead of spending years looking for your great-great-grandfather, spend you time looking for your great-grandfather and finding your great-great-grandfather just might take care of itself.
If you find no information, after making a reasonably exhaustive search, you may be at the end of your line. But I wouldn't think so. I know about only a very, very small number of people who have really searched all the possible records about an ancestor. Don't make comments about how hard it is to find the mothers, please!