In how many ways we can assign a value to local!variable?

Can you clarify what you mean by "all the ways we can assign value to local variables"? I can think of three options:

1. Explicitly declare the value in a load or with statement
2. (load() only) Save a new value to the local variable by using a!save in a saveInto
3. (with() only) Have the local variable re-evaluate due to an interaction with the interface

For a variation on 2 you could have the local variable be an input to a sub rule that does a saveInto to the rule input and therefore indirectly into the local variable... 

To assign a value for a local variable. Below two scenarios are possible

1)  Assign a value during the time of local variable declaration

2) Override the value inside saveInto parameter