Hi all, 

I'm learning triggers in salesforce and want some advice on understanding how to write a trigger for below scenario. what is the approach?
There are two objects Object1_c(Parent) and Object__c(child) having look-up relationship.

Summary:
Object__c has record types namely  "A" and "B".
Object__c has a field (currency) --> Myamount__c
Object__c has 2 picklislts --> Picklist_a__c and Pciklist_b__c
object1__c has a field(curreny_ --> amount__c

Scenario:

when amount__c(on Object1__c) is blank or null, and if record type is either A||B and Picklst_a__c and picklist__b is selected then Myamount__c should be required show be the error.

Thanks in advance.