How can I deal with Stalkers?

Just make it clear to them that you know what they're doing. If it serious enough to be considered harassment, you could get the police involved.

Everyday I used to get bullied at my school. People would throw food at me in the cafeteria for no good reason at all just to be mean to me and constantly bully me for no reason

It is best to ignore them, but it's wise to turn to the police if they become violent or start to bother you severely

Block them from anything that they use to contact you so they can't get a hold of you or be in contact with you.

If they're online, block them and keep blocking them if they are creating new accounts. As for real life, there is nothing much you can do than tell someone and they might take it further like the police. Same thing with online as well, though it will be a lot harder to find this person when they're online and probably creating fake profiles.

Figure out how they could be stalking you. Is it a mutual friend? Is it a social media account? Is it a certain bus route you take everyday to get somewhere? Depending on how they are, different things apply but the thing is to cut the information supply. Change your bus routes (or if you can't leave at an earlier time than usual). Delete a social media account and remake it with a pseudonym. Distance yourself from your friend or tell them your concerns. That's if the stalking is just from a far, though. If it's something like following you home, then that's when you should get law enforcement involved about the risks.

the best way is first to tell them to stop. If they don't stop, contact the police or an agency that deals with stalkers (including your local area's domestic violence agency, which is to the best of my knowledge of a place for you to look for resources).

You should contat the police dpartment and you can get a restraining order so thy will need to leae you alone

Tell someone. If someone is following you. Or creeping around you. You need to get help. If it's really bad. Call the police.

Minimise the time you spend alone when out if you can, report them to the police, keep a diary of their behaviour.