what to do with a middle stack???

Hi everyone!
When u play tournament, somebody told me that u've got to be tight as long as u've got between 20 to 25 times the BB. If u're under 10 times the blinds, u don't have the choice...all in as soon as possible. But when u're under 20 times (10-19 BB),what do u gotta do? Should i play more agressif?

This is the Tournament hand analysis section, your question will get a lot more answers if you post in the strategy section.