First rule is don't open shady attachments. If you get a link or a message from a friend and it just doesn't seem right - don't open it. You should be sure of the origin of the message. If the offer or video is tempting and seems legit, still checkout websites like snopes.com to confirm it's not a scam.
You should verify the item's authenticity. If you're buying from a site like Craigslist.com, you want to make sure the seller is who they say they are. Check and make sure there is a landline listed for a seller and get their name and address before you meet up with them and exchange goods. If it is a retailer make sure they have a website and an address and phone number listed. Also, be sure to pay with a credit card in case you need to dispute charges later.
Check a group's nonprofit status. A lot of charity scams pop up after disasters. You should make sure that the website address is correct and the organization name is correct. Go to IRS.gov/charity to verify the charity's status.
Stick with trusted websites when it comes to home and vacation rentals. Make sure you're not looking at a fake posting where someone has taken a real posting and placed their information on it. Stick with trusted sites like HomeAway.com and VRBO.com which charges home owners a listing fee. Renting through a real estate agency is another safe option.
Use legitimate credit counseling. A lot of companies charge fees without actually doing anything. Stick with a legitimate nonprofit counseling outlet that has an established record of helping people. Also try negotiating directly with your creditor.