Developer: Trigger Design Patterns

Some standards to follow while writing Triggers:

a) Write only 1 trigger per object to handle all scenarios
b) Trigger should not hold any logic--bulk of the logic should be done outside of the core trigger code
     in a seperate class
c) If your trigger has an after update then make sure that you are covering for recursive trigger traps
by using a boolean variable at the start of the execution

Write your trigger with the most basic of codes:

trigger OpportunityTrigger on Opportunity (after insert, after update) {
  if(Trigger.isAfter && Trigger.isInsert) {
    OpportunityTriggerHandler.handleAfterInsert(Trigger.new);
  } else if(Trigger.isAfter && Trigger.isUpdate) {
    OpportunityTriggerHandler.handleAfterInsert(Trigger.new, Trigger.old);
  }
}

Do all the handling in 

public class OpportunityTriggerHandler {

  public static void handleAfterInsert(List opps) {

    // handler logic

  }

}

Over time as your logic increases it will be a lot readable and maintainable.