Some people have a tree with only their direct line and births marriages and deaths. This is OK as far as it goes.
It really helps to have the brothers and sisters as well.
And a good way to track the family is through the censuses. If you can see the same names appearing in the right order with matching birthplaces in the censuses, you know you have the right family. This is particularly helpful for common surnames.
If you can't find a birth record for your ancestor, you may find one for a sibling and that way you can establish the parents' names.