Analysis:
The best advice I can offer here is to say that there are two elements you need to look at - comprehensiveness and coherence/cohesion.
How comprehensive is the idea/book/data/whatever you're analysing? Is it uniformly applicable? Right now I'm reading a report that argues that a 100% tax/publicly funded healthcare system would deliver better patient outcomes. Crucially, the report doesn't take (for instance) mismanagement or fluctuating tax revenues into account so in an assessment I could argue it isn't a comprehensive argument.
How coherent/cohesive is the 'thing' you're analysing? Does that argument it makes seem logical and consistent? How about when it's challenged by competing ideas?
Evaluation:
Use the above to form some kind of idea about whether you agree with 'it' (whatever 'it' is - a person, a book, an academic theory - whatever) and accept it as credible. If you don't, it's not enough to say you don't- for a distinction you're going to need to do independent research to find something to rebuff an original claim and back up your opinion with something that has more academic merit than an access to HE essay.
When analysing or evaluating, don't let yourself get put into a box. Not every source you will encounter will be something you agree with or even see as credible - that's fine.
Source: I did an access course last year and finished with 54 distinction 6 merit.