Be aware that all this steps you have to apply only after you have configured your store. If updates, code modifications, extension installations are needed all this points should be disabled.
Enable all Magento cache: go to System-> Cache Management Select all types and activate them.
“CSS Settings” and set Yes in both tabs.
Enable Flat Catalog: go to System->
Configuration-> Catalog-> Frontend set Yes in Use Flat Catalog
Category and Use Flat Catalog Product dropdown lists.