Before tuning your PostgreSQL database server, work on optimizing some of the key factors in the hardware and the database. All databases, of all types including PostgresSQL and MySQL, are ultimately limited by the I/O, memory, and processing capabilities of the hardware. The more a server has of each of these, the greater performance it's capable of. Using fast disks with hardware RAID is essential for a busy enterprise database server, as is having large amounts of memory. For the best results the server needs to have enough memory to cache the most commonly used tables without having to go to the disk. Under no circumstances should the server start swapping to hard disk. Similarly, the faster the CPU the better; for servers handling multiple simultaneous transactions, multicore CPUs are best.