to beware; to mind; to take care not to do something; to be careful; to take precautions; to watch for something; to be on the alert against/for something
The director asked the salesmen to watch out for forged bank-notes
Be on the watch for pickpockets!; Beware of pickpockets!; Look out for pickpockets!
Police will look out for rioters; Police will take precautions against rioters
in anticipation of something; (just) in case; lest; for fear that; for fear of doing something
To take plenty of warm clothes in anticipation of bad weather/ (just) in case the weather is bad
Prison-breakers tried to tiptoe for fear that/lest the guard might discover them; Prison-breakers tried to tiptoe for fear of being discovered by the guard