Are you sure that "find" is really your ancestor?

Many beginners, when researching their family tree, find a name and approximate date which seems to fit and assume that they have found their ancestor - and stop looking. A recent inquiry relating to someone called William Howard turned up the following entries in the Hemel Hempstead baptismal register which clearly demonstrates why you have to be careful:

It shows that two different babies called William Howard, with different fathers also called William Howard, were baptised in the same church 8 days apart ....

For many more similar examples see 

Right Name, Wrong Body