- Enable all Magento caching layers
- Configure your web server to enable Connection Keep-Alive, enable mod_expire, gzip compression.
- Enable MySQL Query caching.
- Install APC or XCache to cache PHP opcode.
- Install Memcache and configure Magento to store session and cache to memory.
- Install third-party Full Page Cache Magento extension.
- Install Varnish cache server for full page caching on system layer.
Check detailed instruction here: http://www.magentocommerce.com/boards/viewthread/36225/
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