These are actual tips than can improve performance and lifespan of your computer.
Make sure your computer case is clean Dust and hair build-up inside your computer, acting like insulation and trapping heat inside. The result is that your fans are not cooling critical components, such as the CPU, as well as they should. Make sure to clean out your case (with compressed air, a vaccum, or both!) and make sure the CPU fan and heatsink aren't blocked with dust.
Check start-up programs Your computer may be starting slowly because it has many (often unnecessary) programs loading in the background. On a PC, check your system tray (the cluster of icons located by the clock), and make a note of the ones you don't use often/ever. In many cases, you can right click on the icon for the program and change the settings, disabling it from starting with the computer.
Ensure you only have one, effective, anti-virus Running multiple anti-viruses at the same time is not an effective way of keeping your computer safe. In fact, they will tend to conflict with each other, possible even detecting one-another as viruses themselves! The constant background battle between them will slow down your computer immensely. In addition, big-box-brand anti-virus software is particularly bloated, and often no more effective than free anti-virus alternatives.
All other issues If you are not comfortable with following the above recommendations, or still find yourself with a slow-as-molasses machine, call up the local techie student (be they family, friends, or your friend's daughter's boyfriend) - not only will they charge less than Future Shack, but you will get better service, and hopefully encourage a budding passion.