All full questions* require a finite auxiliary verb† (that is, an auxiliary verb tensed for either past or present) before the subject. When the verb in the sentence is a construction with an auxiliary, this is accomplished by switching the subject and the auxiliary. When the verb is a lexical verb with no auxiliary, it is accomplished with DO-support: the tense is removed from the verb and put on a form of DO before the subject:
He is John Smith. → Is he John Smith?
He is [who]. → Who is he?
He has gone to town. → Has he gone to town?
He has gone [where]. → Where has he gone?
You look like an executive. → Do you look like an executive?
You look like [what]. → What do you look like?
Your second sentence, however, confuses two different constructions. There What is not an interrogative, a question word, but a relative pronoun heading a clause which acts as a noun phrase. The statement form would be:
[Subject What you said] [Verb turned out] [Complement to be true].
Consequently, the question form would be:
Did what you said turn out to be true?
* As Peter Flom points out, questions may be truncated very substantially in discourse context.
† BE is always considered an auxiliary, even when it is the only verb.