For us, they are a necessary evil... we make ends meet using them, and pay for my schooling. I am offered both a subsidized and unsubsidized each semester from the Gov. There are private party loans, as well, that you can take out if not awarded enough from the Gov...
DH has loans out from his undergrad, we have consolidated them and are paying on them. I am accuring some from my graduate work right now...
Each school is different. At mine, every student requesting any kind of aid is requred to complete the FAFSA, then the Student Aid Report is mailed to the school of your choosing, they put together your financial aid offers, and you can accept or deny whatever you want. This also includes any grant offers you might get (which of course graduate students don't receive). DH received some grants in undergrad from his FAFSA info.
We often take out a generous amount, stick it in the savings account, and if we dont need it, then it accrues interest and can be used the next year. Since you get one offer for all of one school year, we try to make sure we won't be short for both fall and spring semesters...
I'm not sure that helps much, but just our exp. Feel free to ask any questions you might have =)