Following are various methods, You can choose some or all:
1.The Simplest way is to remove the unnecessary software from computer.
2. A junk cleaner and Computer optimizer can be used to remove temporary files and settings. There are lots of software like CCleaner, tune up utilities, System Mechanic etc. I prefer CCleaner.
3. Defrag your Hard Drive.
4. Upgrade your Physical memory (RAM)
5. Upgrade Processor and MotherBoard.