For instance,
I learned to not dive into an agreement without fully understanding what I was agreeing to: went for a government scholarship that I couldn't get out of without paying money back for them funding my school. I couldn't quit the government even though I was led to believe on limited information that I'd be working at a government research lab versus doing more contract work.
Second, I learned to always make sure to check to see if you need a Visa to get into any foreign country. Me, being young and ignorant, didn't realize I needed one for going to China for 5 days. No one else on the trip told me I'd have to worry about it. I ended up stranded at the Los Angeles airport because I couldn't move any further west without the Visa and spent the night in the airport terminal before taking a flight back with my tail between my legs. The funny part was, I was going to China for a Robotics conference and to be paid for from a poster contest I won at school. In the end with the Visa fiasco, I ended up not going to China, and not getting reimbursed for portions of the trip because of this, so lost $400 overall.
So, #1: Always know what you're getting in to, ask as many people as you can for gathering information before making a decision. Ask questions!
#2: Ask questions again, but always look to see if you need a Visa for a country for the amount of time you're spending there. Planning ahead!
Looking forward to learning through others mistakes!
