Hello Cornishbird, welcome to UsingEnglish!
The two particular problems I've noticed with conditionals generally are:
1. A belief that every "if" statement must relate to one of the conditional types.
Thus if-statements where the condition is granted/accepted, rather than proposed, may cause problems, e.g.
a) If that was MrQ, we ought to leave. ("Why isn't it 'were'?")
2. Puzzlement over certain type 2/type 3 or type 3/type 2 structures, e.g.
b) If he were a little more astute, he wouldn't have made such a stupid mistake. ("Why isn't it 'had been'?")
c) If he hadn't made such a stupid mistake, he would be here with us today. ("Isn't that 'mixed' and therefore ungrammatical?")
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