From your experience as logistics person what are the advises you give to the purchaser to secure the required items from international market ?

Aside from ensuring the correct specs of the item to be purchased consider as well the distance of the source of the items to be purchased.  Provide enough lead time to ensure the items will arrive on time before the date it is required.  Likewise, multiple sources of the items would come in handy specially when your first option has run-out of stocks.  Multiple courier alternatives will also be necessary to ensure no delays or long delays will be encountered during the shipment of the items purchased from the source up to the purchaser or requestor.