Here are some things that are not likely to help performance. They stem from out-of-date information and/or naivety.

• InnoDB has improved to the point where MyISAM is unlikely to be better.
• PARTITIONing rarely provides performance benefits; it can even hurt performance.
• Setting query_cache_size bigger than 100M will usually hurt performance.
• Increasing lots of values in my.cnf may lead to ‘swapping’, which is a serious performance problem.
• “Prefix indexes” (such as INDEX(foo(20))) are generally useless.
• OPTIMIZE TABLE is almost always useless. (And it involves locking the table.)