They are both very common verbs with lots of meanings. For example: KEEP -- to keep something for somebody - guardar algo para alguien to keep something from somebody - ocultar algo a alguien (information) to keep one's job - conservar el trabajo to keep its shape - no deformarse (garment) to keep its color - no desteñir (garment) to keep somebody's attention - mantener la atención de alguien keep the change - quédese con el cambio to keep a diary - llevar un diario to keep a note of something - llevar cuenta de algo to keep order - mantener el orden to keep a record of something - registrar algo to keep a secret - guardar un secreto to keep something clean/secret - mantener algo limpio/en secreto to keep somebody awake - mantener or tener despierto(a) a alguien to keep somebody waiting - tener a alguien esperando HOLD -- to take hold of - agarrarse a to hold something in position - sujetar algo sin que se mueva to hold somebody prisoner - retener a alguien como prisionero the police are holding him for questioning - la policía lo tiene retenido para interrogarlo to hold somebody's interest/attention - mantener el interés/la atención de alguien to hold somebody to his promise - hacer que alguien cumpla su promesa to hold one's breath - contener el aliento

It depends on the sentence.Here's a link http://www.bbc.co.uk/worldservice/learningenglish/grammar/learnit/learnitv292.shtml