Start with definition.
Then give another definition (is a 25 marker so need 2).
Need a diagram (choose most appropriate).
Analysis (integrate diagram e.g. from AD1 to AD2) (A leads to B because... ).
Then do counter analysis (A may not lead to B because... ).
Then another analysis (with a new diagram dependent on what chain of reasoning you follow) (C leads to D because... ).
Then second counter analysis (C does not lead to D if/because... ).
End with evaluation (depends upon xyz / size / cause / time).
A and C are different causes. B and D are different effects. Fill in the chain of reasoning.
For the final evaluation, try to make sure that it's a different point, and don't just use ceteris paribus (unless you REALLY can't think of something else).
Is a generic plan so tailor it to the question.
Hope this helps (I do OCR and our teacher recommends us to follow this for 25 markers).