tener cuidado

'Tener cuidado' could be also translated (from what I know) as ' to be careful', or a bit more literally, 'to take concern' or 'take care' about something.

Usually, you use the phrase to warn somebody before something, not precisely beneficial, happens to them:

• ¡(Tú) ten cuidado con el monstruo bajo la cama!
  (You) be careful with the monster under the bed!
• (Ustedes )tengan cuidado con el clima en la montaña. Puede ser engañoso.
  You (guys) take care about the mountain's weather . It can be deceitful.