If you mean buying through QL without meeting seller and checking item... then Never ever buy through QL.

These simple rules you might find helpful,
1. Contact buyer through phone only and make sure seller is in Qatar.
2. Item he/she is selling is thier own peoperty. (Proof is always better).
3. Currency of transaction should be Qatari Riyal.
4. Never send money or your personal details to anyone.

Now a days there are lots of spammer and cheaters using QL to cheat innocent people. Be Careful!!!

Wish you best of luck