I do not remember ever having confusion over this. I think it is normally self explanatory.
Brackets/parentheses take precedence over everthing else.
But I would think of 6! as an individual number. So 5*6! would mean 5 * the factorial of 6.
If that doesn't help maybe you can give us specific examples that are confusing you.
The order of operation that I still get confused with is a power of a power
Is that 3^16 or is it 81^2
There is a rule but I always forget what it is.