Understanding which words to capitalize in German is, for the most part, easier than English. In German, all nouns are capitalized. There are, however, a few cases where words that at first appear to be nouns are not capitalized. When used with the verbs sein, bleiben, or werden, the words angst, leid, pleite, recht, and schuld become predicate adjectives and are written lower case: 

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Sie hat geantwortet. „Lieber Unbekannter, Sie haben völlig recht.“

She replied. "Dear stranger, you are absolutely right".

Caption 43, Die Pfefferkörner - Gerüchteküche

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As a noun, the word das Recht is written starting with upper case, but in this case the word recht is in fact a predicate adjective, not a noun. If you deconstruct the sentence and replace recht with a noun, it is immediately clear that the sentence makes no sense with anything but an adjective.
 

Aber hey, ich bin nicht schuld dran, ganz bestimmt nicht.

But hey, I am not to blame for it, definitely not.

Caption 55, Rapucation - Guten Appetit

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Here again, in some expressions with the verb "to be" (sein), what may appear to be a noun is actually a predicate adjective. So other than these few exceptions, capitalizing nouns in German is easy. If only noun genders were so simple! 

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Further Learning
Read more here about the rules of German upper and lower case. Search on Yabla German for forms of the words listed above in a real world context.