1) NEVER give out your credit card information. You should not have to pay to work for someone.
2) Do research on the website to be sure. Check ripoffreport.com or search the website in yahoo.answers.com to see if people are speaking positively or negativity about them.
3) Use your head. Is a company really going to give "$300 a day" to an amateur who has little to no experience with computers? No.
Below are a list of legit, work at home jobs that I have joined. They are all 100% free to join.
MTurk: [Paid] So far the best why I make money online completing surveys and simple tasks. I can make up $5 a day when I really buckle down and and focus for at least 3 hours a day.
InboxDollars: [Paid] Get paid to read email, take surveys, complete offers, and refer people. Minimum payout $30.
InstaCG: [Paid] Earn points completing offers, watching videos, shopping and more on InstaCG. It's a fantastic alternative for me then getting an Amazon credit rewards card. I shop on Amazon all the time and get 2% cash back.
Swagbucks: [Never/Not paid but earn a little] Redeem awesome prizes by earring Swagbucks by doing simple tasks like completing offers, watching videos, taking surveys, cutting coupons and more.
Cashcrate: [Never/Not paid but earn a little] Get paid to complete surveys, and free offers.
LUUUX: [Never/Not paid but earn a little] Earn LUUUX dollars by simply posting your blog entries, commenting, sharing link and lots more easy things your probably already doing on the internet.
CashCrate: [Never/Not paid but earn a little] Making money by completing offers, taking surveys, and shopping online.
Make money selling
In my personal experience online, I have earned more selling items then participation in survey websites.
Etsy: [Paid] I have been selling my handmade creations on Etsy since 2009.
Amazon: [Paid] A great way to make a few bucks a month. Only sell new, or gently used items.
Ebay: [Paid] Another great way to make a few bucks a month. Although, they have monthly fees.