As a logistics service provider, how do you minimize cost while offering a high quality of service?

By keep improving / searching for an alternative equipment, tools, manpower and all facilites around, which can make the efficiency (at least the same) if not better, WITH a lower costs.
That can be done only once the logistics provider is controling his work and already approached a level of confident where he is free to look for extraordinary things to be developed and reviewed (better than what can be provided normally) and that is an advance stage of experience and self-organizing.
Regards,

Dear, Its depend on following: Availability of good with shipper on time Availability of shipping documents on time You should have 3 freight forwarder quote (Reliable freight forwarder) lead time of freight forwarder to move goods from origin to destination.

To become successful in the market, offering the right product for the right price is just not enough anymore.
Corporate must do it at the right place in the right time and in the right configuration.
So, it's essential to set-up an effective and efficient supply chain, tailored to the unique characteristics of your products, service levels and markets.
Hence, in my view and based on my previous experience with one of the leading FMGC, I believes you can consult an expertise Or Fourth Party Logistics (4PL) to handles and manages your supply chain and logistics services.

I’m assuming you are asking this from a service provider’s perspective....
In the logistics business, cost and efficiency go hand in hand.
To be more precise, they are inversely proportional: Inefficiency leads to additional costs.
Most costs are incurred in the ‘last mile’ phase of the delivery lifecycle.
Repeated delivery attempts (when the recipient is unavailable) is a huge contributor.
This is why most couriers shy away from B2C deliveries, or ones that do, charge a premium for it.
A pro-active approach to keeping recipients well informed and updated with tracking info is key.
At SwipeZoom, we send several notifications to the recipient keeping them abreast of the exact date and time of delivery, reminding them and giving them an option to reschedule, at various important milestones of the delivery lifecycle.
This increases efficiency and lowers costs.
Similarly, incorrect addresses can also add a layer of additional cost, albeit less than repeated delivery attempts.
We use an address verification system at the time of booking the shipment, which helps ensure that we are capturing a valid address, regardless of the destination.
The above are just a couple of the most important areas where service providers incur additional costs.
Addressing these issues will help lower costs and automatically increase efficiency.

Have enough experances in Operations research and managements. 

I think the answer to this is different depending on what type of logistics service provider you are.
If you are a freight forwarder, the key to providing high quality service at a low cost seems to be in specialization.
By specializing around certain lanes a forwarder creates the opportunity to be more efficient while also being able to leverage cost savings through bulk purchases of space on planes, ships, or other modes of transportation.
For an integrator, volume and network efficiency (hub and spoke in the air cargo arena) seem to be the keys to providing high quality service at a good cost.

dear Reem , i'll be more than happy to answer your question ,in order to best help you please be kind enough to provide me with more details on your case such as ;
1- logistics field your are working in
2- transportation or freight means used (air / land / sea )
3- service provided ( local / international )

1- cocept of cost: A-choosing the means of transportation direct and indirect cost in lower level.
B-choosing suitable customer service.
C-choosing number of warehouses.
C-choosing safety stores levels.
D-choosing following operation for multiple products.
2- multiple and excellence distributions.
3- mixed strategy.
4- postponment.