Ann is right - identify the queries that are the worst offenders and see
if you can tune them.

What are the indexes like? A good compound index can make the
difference between a complex query finishing about the time the sun goes
nova and finishing instantly. Can you add a term to the query to force
it to use a better index?

Are you getting a lot of deadlocks? Deadlocks actually hit your system
performance at least three times - the initial query, the rollback, and
then the re-query.