How to identify a noun clause in a sentence.

"A dependent clause usually begins with a dependent word. One kind of dependent word is a subordinating conjunction. Subordinating conjunctions are used to begin dependent clauses known as adverbial clauses which act like adverbs. In the following examples, the adverbial clauses are bold and the subordinating conjunctions are italicized:

Wherever she goes, she leaves a piece of luggage behind.

(The adverbial clause wherever she goes modifies the verb leaves.)

Bob enjoyed the movie more than I did.

(The adverbial clause than I did modifies the adverb more.)

Another type of dependent word is the relative pronoun. Relative pronouns begin dependent clauses known as relative clauses. These can either be adjective clauses, which act like adjectives, or noun clauses, which act like nouns. In the following examples, the dependent clauses are bold and the relative pronouns are italicized:

The only one of the seven dwarfs who does not have a beard is Dopey. (The adjective clause who does not have a beard describes the noun one.)
No one understands why experience is something you don't get until just after you need it. (The noun clause why experience is something you don't get until just after you need it functions as a direct object.)

A noun clause can be used like a noun. It can be a subject, predicate nominative, direct object, appositive, indirect object, or object of the preposition. Some of the words that introduce noun clauses are that, whether, who, why, whom, what, how, when, whoever, where, and whomever. Notice that some of these words also introduce adjective and adverbial clauses. To check whether a clause is a noun clause, try substituting the appropriate pronoun (he, she, it, or they).
Examples:
I know who said that. (I know it.)
Whoever said it is wrong. (He is wrong.)

Sometimes a noun clause is used without the introductory word.
Example:
I know that he is here.
I know he is here. (without "that")

In some cases, use of the introductory word, though grammatically correct, may sound cumbersome in English.
Example:
I think that it is pretty. (correct, though excessive)
I think it is pretty. (standard usage) "
Source and further information:
http://en.wikipedia.org/wiki/Dependent_clause