Follow the 3-section format (problem; alternatives; recommendation/rationale).
Don't use more than a sentence or two re-stating the facts of the case in your problem statement. Use facts from the case in the third section to defend your recommendation. A one-sentence problem statement is sufficient. Two sentences are plenty.
In the third section, take a stand
Focus on convincing the reader why your recommendation is a good course of action. Spell out the reason(s) clearly.
Good memos make liberal use words like "because" and "therefore" in section 3 because these words show the relationships between facts (e.g. observations from the case) and conclusions/recommendations.
Don't feel that you must come up with an elaborate, novel recommendation. It is OK to focus on analysis of some of the straightforward options and defending a straightforward recommendation.
Don't make your options or recommendation too broad or general. A recommendation like "implement TQM" or "implement CPFR" is probably too general (especially given the cost, difficulty and risk involved in implementing such sweeping changes). It would probably be more useful to pin-point specific elements of TQM or CPFR that might make sense in the particular situation.
In the third section, it is useful to anticipate and defuse counter-arguments--or at least acknowledge these as weaknesses of your solution.
Don't equivocate. Avoid clauses like "I feel that" & "I believe."