Tethers Are Your Friends
Your grappling hook does more than just get you around. It can be used to create tethers between any two things, even if one of the things can’t be moved. You can use this to save yourself bullets or to do some really neat tricks. It’s possible to destroy just about everything in the game using this nifty gadget and it will help you out a lot when taking over bases and outposts.
The only time tethers will be useless in Just Cause 3 (at least early on) is when trying to take out extremely large Chaos Items such as those huge satellites, or large communication towers (the ones with all of the radio receivers on them). But everything else is fair game as long as you give it enough leverage. Don’t be afraid to use all of your tethers on one item to ensure destruction.