How to add Shipping method for commerce flat rate module? i am working on drupal commerce's "shipping" part, i want to create two methods for shipping as 
1.Free Shipping 
2.Express 2-day Shipping 
for USA .

For "free shipping" condition is if order total is greater than $100 then we can use "free shipping" else it should apply rate $4.

for "Express 2-day Shipping" condition is if order total is less than $140 then we  can cost $12 else it is free.
The Rules module integrates with Drupal Commerce in order to handle this type of requirement. There are many video tutorials available that explain how to setup various shipping rules.

There is also a module called Conditional Rules that may be useful if you need to have branching logic in your rules.

In this case I think you would only need two rules:


Conditions: type of shipping == "Free shipping" AND order total > $100 Actions: shipping cost = $0
Conditions: type of shipping == "Express" AND order total > $140 Actions: shipping cost = $0


You would set the default pricing for the "Free shipping" to $4 and the for the "express" to $12. The default prices would be overridden by the Rules in those two cases.