1. How long has the property been advertised? The longer it has been on the site the more likely it is genuine.
2. Use maps.google.com to confirm location and, if possible Street View to see if property matches the picture on line.
3. Speak to the owner on the phone, preferably land line which gives more security than a mobile.
4. Ask the owner for their postal address and don't sign a contract without it.
5. Ask the owner about the property and area to judge their knowledge and trustworthiness.
6. Be wary if the price seems too good to be true.
7. Don't pay until you get a written contract including terms of any security deposit which should not be disproportionate ( 10% of rental is reasonable)
8. Avoid untraceable money transfers such as Western Union. Credit Card is safer.
9. Check the property on arrival and alert owner of any damage.
10. Get any security deposit back on leaving the property and if deductions are made ask for proof such as receipts.
Most of all be alert and use common sense.