The reflexive pronouns (which have the same forms as the intensive pronouns) indicate that the sentence subject also receives the action of the verb. (Students who cheat on this quiz are only hurting themselves. You paid yourself a million dollars? She encouraged herself to do well.) What this means is that whenever there is a reflexive pronoun in a sentence there must be a person to whom that pronoun can "reflect." In other words, the sentence "Please hand that book to myself" would be incorrect because there is no "I" in that sentence for the "myself" to reflect to (and we would use "me" instead of "myself"). A sentence such as "I gave that book to myself for Christmas" might be silly, but it would be correct.
Be alert to a tendency to use reflexive pronoun forms (ending in -self) where they are neither appropriate nor necessary. The inappropriate reflexive form has a wonderful name: the untriggered reflexive. "Myself" tends to sound weightier, more formal, than little ol' me or I, so it has a way of sneaking into sentences where it doesn't belong.
Bob and myself I are responsible for this decision.
These decisions will be made by myself me.
If you have any questions, please contact myself me or Bob Jones.
When pronouns are combined, the reflexive will take either the first person
Juanita, Carlos, and I have deceived ourselves into believing in my uncle.
or, when there is no first person, the second person:
You and Carlos have deceived yourselves.
The indefinite pronoun one has its own reflexive form ("One must have faith in oneself."), but the other indefinite pronouns use either himself or themselves as reflexives. (There is an entire page on the pronoun one.) It is probably better to pluralize and avoid the clumsy himself or herself construction.