What should a parent do to a toddler who always screams or cries if he doesnt get what he wants?

It depends how old the toddler is, and whether he can talk! Whichever it is, you can adopt the peaceful parenting method of acknowledge, explain, choice. Acknowledge why your son is feeling that way - it could be because he wants a toy, he wants to go somewhere else or doesn't get what he wants to eat etc. Anything! Get to his eye level and say things like "Are you upset because ____?" Pause and wait for some kind of response, sometimes it also helps to carry him to keep him calm because they can't hear you when they're screaming their heads off - you may also use firm and calm tones of things like "Mummy/Daddy doesn't want to talk to you until you calm down". After acknowledging his feelings, explain why he can't get what he wants - be it because he already has the same thing at home, it's not healthy, he's sick so no snacks, you can't afford it etc. The key is to keep it simple and keep it honest! Finally, the step that most parents forget is the choice - give alternatives to him as to what he CAN do instead. Eg. if it's something you cannot afford, either tell him you'd get it another day (give a time period like next week/when you get your pay) or show him the choices that you can afford to buy for him. Whatever you end up saying, make sure you keep your word and fulfill it! The other important thing is to remain calm throughout, and be consistent in the way you address such situations, your tone and your actions. It helps to also enforce this as early as possible, and it does work if you keep it consistent!