Any number of things:
1. Read newspapers with great, growing discernment. The more you read, the more you'll know and realize that which is mere opining vs. mere factual.
2. Watch the news (and more than ABC, NBC, CBS, CNN). Same applies as in #1, especially w/ mainstream. They are increasingly in entertainment biz vs. journalism.
3. Talk to your teachers and others who should be interested in the goings on in the world. Probe how they've come to their perspectives.
4. Occasionally read USNWR, Time type things but don't quote them too much. They tend to have their POV and be very shallow, imo.
5. Read the Wall Street Journal. It's way beyond financials.
6. Identify key syndicated columnists, commentators, and authors who are really bright, insightful ... I like Sowell, Krauthammer, Will, Gaffney, etc.
7. Read good books.
8. Be discerning in recognizing the POV, i.e. where your informant "stands" be they left wing, conservative, in-between. Initially you won't be much able to tell the difference. Soon you will.
9. ID some on-line sources you appreciate and read them regularly. And read the opposign POVs. Think and make up your own mind.
10. Always recognize that you see the world thru you own glasses. They are yours alone to search for truth.
11. Find reliable older mentors, people who can be trusted and will bring maturity and experience to youthful enthusiasm and naivete. And lean on them, milk them for all they'll give you. And remember, even these are not God. God is god.
Of course we should ask questions, but asking the question which is essentially "should I ask questions" is well, questionable. And at least naive. And if it's asked by one older than 10 or 12? Likely different term for that status.