The best answers come from measurable data, don’t let the “I think that “, “I believe”, “IF…” drive your decisions when it comes to performance.

Where to look? Well, don’t try to reinvent the wheel, there are plenty of tools that can provide enough data so you can make informed decisions regarding mysql performance.

SQL Performance Tips: There is lack on benchmarks about most of the suggestions here, still, many of them are obvious and can help you about what to test.

How to profile a query in mysql: this is self explanatory :)

Using the New MySQL Query Profiler: SQL diagnostic tool that assists in the debugging and analysis of running SQL.