Dative is a Russian grammar case that expresses action is addressed or referred to the object you are speaking about. Here I'll try to explain the order of forming it. Mother gave а bottle of water to (WHOM?) her child. Мама дала бутылку воды (КОМУ?) своему ребенку. Here the word "Ребенок" was used in a dative case "РебенКУ", because the action that mother did ("GAVE") was addressed to some object ("CHILD"). In dictionaries all the words go in Nominative. So, to make a dative form of it, you should learn the rules of changing the word's ending according to its gender and form (singular or plural). It's a difficult thing to explain in two words. Hope my answer was helpful.

+ Кроме того, дательный падеж используется после предлогов «к», «по», «благодаря»: Я иду к другу. Мы гуляем по Невскому проспекту. Благодаря твоей помощи я сделал работу вовремя.

Dative case has such questions to the object, as --- to give wich ? to give what?