(a) Outline the link as to why you are solving the case, read all evidence and look for suspects and motives whilst trying to find as many alibis to rule out people.
(b) Make note of motives, evidence, and alibis – read all evidence, work out motives and evidence linking to them and what their alibi is/could be. An alibi can rule out a suspect, just make sure the alibi is correct by cross-referencing evidence and reading all information (any conflicting evidence could be a problem).
(c) Work out a timeline of events – using the provided evidence to place each suspect (and mentioned characters) throughout the night of the murder. Again, be wary of conflicting evidence.