Whatever resources you have at your disposal, however good your research skills, there are going to be times when you come up against a brickwall and can’t get beyond it. Maybe you have an ancestor with a common name, and 500 Mary Jones to distinguish one from another. Maybe you can’t find out where you ancestor was born and so can’t track down his parents? Maybe there’s a gap where your ancestor should be.
The first thing to do, is to see if you can gather any information by following the family tree horizontally. That is, look at your ancestor’s brothers and sisters, uncles and aunts. Were they witnesses at weddings, sponsors at baptisms, involved in legal cases? Can you gather any information from other members in the family at all?
Then try researching the place your ancestor came from, if you know it, or the last place you have associated with him or her, and the period you are looking at. It’s often useful background information anyway, but you never know when some family circumstance or local event will illuminate the path. I researched the people who used to attend the Quaker Meeting House in Uxbridge at the beginning of the 19th century, when people were beginning to move into cities and towns, and suddenly found one of the families doing the opposite – moving to Scotland only to die there shortly afterwards. Researching the things that were going on at the time, I found that nearly all of their relatives had died of a fever that was spreading like wildfire in London, and they had fled to Scotland to avoid the infection, only to take it with them and die, one by one, in Scotland.
So, look at local records, find out what sort of an area they came from, what industries were common, whether any national events were likely to affect that trade. Local newspapers often have an archive available in the local studies centre of your local library. The Victoria County History, a massive project which hoped to record the history of the people and natural environment for every county in Britain dedicated to her then longest-serving Monarch, Victoria, may have useful information, depending upon the coverage for your county.
Local history societies (there’s a useful list here) and family history societies tied to the place you are interested in, may well have information which is useful. The Federation of Family History Societies offers a find-a-society link on their website. There’s a British Association for Local History too.
You may find it helpful to get another family historian to look at your research, to see if they can make suggestions for you. All of us can be blind to a detail which another may see clearly. Sometimes someone coming fresh to the problem will see something you have missed. I also find it useful to leave the problem for a while to pursue other lines of inquiry, as coming back to it fresh may also give you a different perspective.