As a purchasing officer how do you made negotiating to different valued suppliers to give a quotation price as a lowest price .?

I believe that open negotiation with suppliers to get the lowest price would lead to disastrous results for the buyer esp in terms of quality and contract execution. So I would prefer to disclose my requirement and all terms and conditions to all bidders alike in transparent manner and let them offer me their final price without any room for negotiations.

That really depends on so many things it's uncanny! What you are buying, how critical it is to you, how many suppliers are out there, how well national economy is doing, vendor's current situation and outlook etc etc. A skilled negotiator should prepare well, know as many variables as possible and be able to artfully utilize everything he knows in a dynamic setting of a negotiation.

PS I believe anyone dealing in purchasing of significant volumes should attend a world class negotiation training. One I can recommend (for having participated in it) is THE GAP PARTNERSHIP negotiation training (Complete skilled negotiator or Essential negotiator, both will do, and second one is a little less expensive).

Thank you for invitation, However the question is totally not clear.