You have to capitalize everything is a noun or act as a noun: substantivized adjectives and verbs used as nouns, but pronouns. You have also to capitalize the personal pronoun "Sie", used as formal you, it's declinations and it's possessives.

I won't be 100% accurate with my answer, but an easy way to learn, think as every word that has a "Der/Die/Das" as capitalized.

Start writing Notebook entries and you will learn the rules as your text will be corrected. Learning by doing :)