What is the criteria for knowing if a certain shipping company provides the best services, best prices and security to your products?

First of all you should investigate about the carrier reliability, transit time etc as mentioned by Ahmad Kaheela. These can can be checked through CARRIER RANKINGS, such as CMA CGM stands3rd while WAN HAI stands39th. 

Similarly you must also check Liner charges at Loading and Discharging ports, B/L Endorsement charges, and many such things which can either make life easier or worst for you. 

The low prices offered by shipping agencies or owners or owners representatives dont mean that you should choice/offer same to the client.you have to investigate about the carriers.THE MAIN POINT is the delay, the transit time and not the price because the client wants to be sure about the arrival's date of the ship or kraft or trucks.

1) Always look for best T.T. and avoid Transhipment.

2) Rates and services are alomost the same now adays, it may differs in method of payment, credit, or date of issuing the B/L

IF YOUR QUESTION ASKED BY CLIENT YOU`LL JUST ASK ABOUT TIMING, PRICING,  ALLOWANCE TIME OF CLEARANCE AND DEMURRAGE AFTER DELAYING, YOU NEED ALSO TO MAKE ASSURANCE POLICY FOR YOUR SHIPMENT FOR MORE SAFETY.

IF YOUR QUESTION ASKED BY PROFESSIONALS YOU`LL ASK ABOUT MANY CONDITIONS, AS EXAMPLE IF YOUR SHIPMENT IS FOOD PRODUCTS YOU`LL ASK ABOUT TEMPERATURE AND HUMIDITY FOR GOODS AFTER PACKING.

YOU AS CONSIGNEE MUST FOLLOW UP THE ARRIVAL SCHEDULE AND KNOW WHO WILL PAY FOR ANY DELAY  OF THE SHIPMENT ON THE WAY TO LAST DESTINATION .