Prevent multitasking. The more apps that are open, the slower your iPad will be. Close all apps that you are not using. BONUS: by closing all unused apps, the apps that are used will glitch less.
Put the brightness to the lowest setting. Not only will this make your iPad quicker, it will waste less battery.
Delete any extra pictures/unwanted pictures/doubles/ect. in your albums.
Save all of your pictures on your PC/laptop/USB/ect. and delete them on your iPad.
Delete any unwanted/forgotten apps.
Update all apps (because bugs sometimes make your iPad glitchy and slow).
When a new iOS comes out, UPDATE IT ASAP!
If the iPad is still slow, consider sending it to a shop to repair it, or if you're short on money, at least for them to check it out. Better safe then sorry!
Your iPad is now faster!