Macroeconomics- Need help being able to discuss fiscal policy and it's challenges

I need to get a better understanding of fiscal policy, including:
1. What actually is fiscal policy,
2. How does fiscal policy work (how is it implemented and enforced, or measured, monitored, adjusted and controlled), and
3. In the context of disussing the topic of fiscal policy in a macroeconomics class, what are some problems, challenges, or concerns that may arise from it.

I have an exam in about two weeks and I'm trying to augment my text reading with more of a third-party tutoring of the above concepts in fiscal policy.  I think I have the basics down, but I'd like a more in-depth explanation.  I already have an additional textbook on the topic and have done some online reading, so please give me a fresh perspective on it... I've read the books already-- I need a more in-depth "Plain language" tutoring on the topic in the context of macroeconomics.  Thanks.