What criteria would you use to select Web transactions for load testing?

What criteria would you use to select Web transactions for load testing?  
 
Eg: Login Scenarios, Buying from a website 
flight reservation,booking a flight etc. 

this again comes from voice of customer, which includes what are the very commonly used transactions of the applications, we cannot load test all transactions , we need to understand the business critical transactions , this can be done either talking and getting details from the client or if it is existing application we can analyse from the webserver logs which URLs has common hits, these needs to be coverted into transaction and the based on the traceability we need to select the web transactions for load testing.

1.What criteria would you use to select Web transactions for 

load testing?

      We can select web transactions from task distrubtion diagram and transaction profile.

From transaction profile we can come to know what are all the major transactions taking place in  a particular day,at what time of the day there will be a peak load etc..

From task distrubtion diagram we can come to know for which transaction there will be more database activity and risk.

once the transaction is selected from transaction profile and taskdistrubtion diagram ,we will perform loadtesting for that particular transaction.

select web testing option  in add-in

we can select web transactions from task distribution diagram and transaction profile.