In C, there are a few rules to follow when naming variables:

Variable names can only contain letters, digits, and the underscore (_) character. They cannot begin with a digit.

Variable names are case-sensitive, which means that "age" and "Age" are considered to be different variables.

Variable names cannot be the same as keywords or predefined identifiers in the C language, such as "int" or "main".

Variable names should be meaningful and descriptive, to make it easy for other programmers to understand the purpose of the variable.

Some naming conventions in C are:

• Variable names should start with a lowercase letter and use camelCase notation for multiple words.
• Constants should be written in uppercase and use underscores to separate words.

It's important to keep in mind that while these are the standard naming rules and conventions for C, different teams, projects or companies may have different naming conventions.