When do you use the counter positive on logic section

[divencenzo]

How many different types of questions are there in the logic section? and of that which use the CP and is there a better way?

[EarlCat]

The number of question types depends on how specifically you classify them.  The number is in the neighborhood of 15 or so, but someone might, for instance, group "must be true" and "most strongly supports" questions into the same category (e.g. "Inference").  Others may define them as falling under different categories (e.g. "Strong Inference" and "Weak Inference").

Whether to use a conditional statement and/or the contrapositive is not always determined by the question type.  In main point questions, you generally can ignore conditionals altogether.  In parallel questions you almost always have to deal with them, and sometimes with their contrapositives.  In other question types, their use may depend on whether there even is a statement of a conditional or causal nature in the argument.  Even then, sometimes it's not necessary to worry about it or its contrapositive.

[Graeme]

It's hard to say.  As EarlKat mentions, parallel reasoning quesitons almost always need them.  Inference questions (must be true), and sufficient assumption questions (The argument would be good if which one of the following were true) are likely candidates. 

A better idea though, is simply to learn how to use it, in writing.  Then don't use it.  I barely write out contrapositives anymore, but I am doing a lot of them mentally when  answering questions. 

Writing it out is a useful tool to help you think logically, and can be a bit of a chore while you're still learning.  But eventually, your goal should be to be able to think about it intuitively.