Genealogists categorize data in three different classifications and you should document how you would classify your finding upon review of the material because, without question you will refer back to it at some later date and may want to know just how sure you were of the goldmine of information you found.

(0) - Sources where speculation and/or supposition hold the reliability of the data in question. For example, if we know that Uncle Harry was born in 1924, but we don't know any other information, siblings of his, or his parents birth dates, we might speculate that his parents were born in about 1900. But that's all this is, unsubstantiated speculation and should be treated as such with great care!;

(1) - Secondary Sources are those which provide data that has been copied from other sources and/or at a date later than the occurrence of the event itself (ea. birth dates found on a marriage or death certificate). Secondary sources of information, such as local histories, can be a tremendous guide for you but beware that articles in them are often biased depending on the writer; and

(2 and 3) - Primary Sources are those which provide data from original documents and/or entries made at the time of the event (e.g.. entries made in the family bible at the time of the event). These are usually the most reliable, but even with them, keep an open mind!! Only record source information as a type 3 (the highest classification) when you have multiple confirming pieces of evidence. With the preponderance of the evidence cases, evidence is unsubstantial to class the overall category as completely reliable.

Don't be afraid to change your classification of the material later on if you find it necessary. You may find later in your research that the information on the birth certificate for Uncle Harry, for example, wasn't as reliable as first thought!!