1. Pay attention to the whole family.
Census records, probate records and deeds, among other records, often name at least the wife, if not additional family members. Identifying other family members in connection with the person you are researching is a great way to confirm identity. Even when the names of other family members are unknown or unavailable, it still might be possible to identify an individual in relation to their family. For example, in the pre-1850 federal census enumerations, where only the head of household is named, by adding or subtracting ten years from the age ranges counted within the household, you can reconstruct the family as it would appear in later or earlier records.
2. Pinpoint the location.
Be sure to know the geography and jurisdictional history of the county, and where your subject fits into it. One case researched by this author involved a pair of unrelated men apparently bearing the same name, living in the same county. But these two men lived quite far apart: one in the far northern part of the county and the other in the southern part of the county. By pinpointing the location where each of them owned land, their separate identities, and eventually the identities of their parents, became clear.
Another way to discover the exact location of an individual is to identify the subject's neighbors. Their neighbors may appear listed nearby in the census or on a map, may be named as adjoining land owners in the land description of a deed, or may appear serving as witnesses or sureties on bonds or other records.
3. Verify the age range.
It often proves to be the case, when two men bear the same name, that one is significantly older than the other. Check the ages, where possible, but even approximate age ranges when the exact age cannot be discerned. Was one actively purchasing land or paying taxes when the other was still a minor? Be sure to note this.
4. Take note of nicknames or other designations.
Believe it or not, the "same name" trap could befall our ancestors, even while they were still living. For this reason, in many records they might be identified with certain specific terms or nicknames to distinguish them from others with the same name. Among these distinguishing monikers might be the terms "Junior" and "Senior," etc., or an associated place, an occupation, or their father's name (or even their mother's!).
The signer of the Declaration of Independence was just one of several "Charles Carrolls" living in Maryland at the time. Legend has it that he initially signed the Declaration simply "Charles Carroll," whereupon one of the other signers remarked that he would be safe because the British would never know which Charles Carroll had signed. Carroll proceeded to add "of Carrollton" to his signature, and replied that there would now be no confusion. From this point forward, he is known as "Charles Carroll of Carrollton" in all records, and is therefore easy to distinguish from the various other Charles Carrolls living in Maryland at that time.
One thing to be careful of, however, is the use of the terms "Junior," "Senior," "III," and other designators of this nature. Unlike the modern usage of these terms, almost exclusively denoting fathers and sons bearing the same name, up through the end of the nineteenth century they were often used even when the two individuals were unrelated! With this historic usage, the term "Senior" simply meant the eldest man by that particular name; "Junior" meant the second oldest; "III" meant the third oldest, etc. To make things even more confusing for today's researchers, when one of the men died, the younger ones were all "promoted," and "Junior" became "Senior," the "III" became "Junior," and so forth. Be on the lookout for this occurrence.
In your search for information concerning your ancestors, you will presumably find your ancestor's name in documents from his lifetime. Establishing the identity of the name in these records is vital to your research, to avoid the "same name" trap. These four steps will help you to spot clues that will keep these separate individuals separate and keep the brickwalls from building up in front of you.