A common mistake in C++ programming is typing = instead of ==. This can be due either to a typo error or because you are used to other languages such as VB that do not have different operators.
An easy way to make the compiler signaling those mistakes is to always set the compared constant value at the beginning.
For example, type:
if (5 == a)
if (a == 5)
The compiler would not compile (5 = a) because you cannot assign a value to a constant.