Buying items from suppliers require a few steps.
The first step is grouping the items that you want to buy, for example, machinery items, probes, and safety items.
The second step is making lists of suppliers for each group. There should be more than 5 suppliers in every list. You can see suppliers classifications - classifications of supplies based on their products- as your reference.
The third step is sending bidding invitations to the supplier and giving them the due date.
Two days before the due date, you have to remind them by sending an e-mail or making a phone call.
After five days, the next step is analyzing process and specifications of items which are listed on the quotations. You have to choose the successful supplier who gives the lowest price and has same qualifications with items that you need. Sometimes, the successful supplier can be more than one.
The last step is making the contract. At this step, you have to ask confirmations from the suppliers and user regarding the prices, delivery schedules, and specifications on draft contract. You have to make sure that the suppliers prices are lower than the budget and their qualifications are the same with what the user wants.
Please note that the user shouldn't know the names of suppliers and their prices. This is necessary to avoid some deceptions. If both agree with the draft contract, you can make the contract and send it to the suppliers. The task seems easy but it does require honesty and carefulness.