MISCELLANEOUS PRONOUNS

alguien: someone, anyone
nadie:  no one, nobody
algo: something, anything
nada: nothing
cada uno(-a):  each (one)
todo el mundo:  everyone
quienquiera:  anyone (at all)
cualquiera: anything (whatsoever)

Remember that the pronoun forms referring to people [such as 'alguien' and 'nadie'] require the use of the personal 'a' when occurring as the direct object of a verb. Also keep in mind the rule for forming negative sentences: one negative word must occur in front of the verb (others may follow the verb).

Examples:
Buscas a alguien?:  Are you looking for someone?
No. Yo no necesito a nadie.:  No. I don't need anyone.