There are many different sytles/conventions that people use when coding C++. For example, some people prefer separating words using capitals (myVar or MyVar), or using underscores (my_var). Typically, variables that use underscores are in all lowercase (from my experience).
There is also a coding style called hungarian, which I believe is used by microsoft. I personally believe that it is a waste of time, but it may prove useful. This is were variable names are given short prefixes such as i, or f to hint the variables type. For example: int iVarname, char* strVarname.
It is accepted that you end a struct/class name with _t, to differentiate it from a variable name. E.g.:
class cat_t {
...
};
cat_t myCat;
It is also generally accepted to add a affix to indicate pointers, such as pVariable or variable_p.
In all, there really isn't any single standard, but many. The choices you make about naming your variables doesn't matter, so long as it is understandable, and above all, consistent. Consistency, consistency, CONSISTENCY! (try typing that thrice!)
And if all else fails, google it.