keep one's eyes open

English Thesaurus

1. pay attention; be watchful (verb.perception)

hypernym	:	look out, watch, watch out,
definition	:	be vigilant, be on the lookout or be careful (verb.perception)

domain usage	:	colloquialism,
definition	:	a colloquial expression; characteristic of spoken or written communication that seeks to imitate informal speech (noun.communication)