Well I'm sure your trainers will ask you about this subject, use
your local knowledge and SOP as a guide, just be prepared with an answer, don't forget to mention the fact that you will also consult your FO

. If your at a top notch operation they will usually include extra fuel, if it's a tankering sector, know how to compute this. How much fuel do you burn during an approach and missed approach, questions, questions. I wish some one like
Old Smokey or
411 would speak up.