Hi,

There's no defined pattern as such but it is always considered as a best practice to have all your trigger logic inside one handler class and only have one trigger on each object.

Example Trigger

An Apex Trigger should be written so that every operation calls a method in an external Apex Class. By doing so code can easily be added or removed, and variables can be used multiple times without additional queries to the database.

trigger objectTrigger on Object (after delete, after insert, after undelete, after update, before delete, before insert, before update) {

    objectTriggerHandler handler = new objectHandler();

    /* Before Insert */
    if(Trigger.isInsert && Trigger.isBefore){
        handler.OnBeforeInsert(Trigger.new);
    }
    /* After Insert */
    else if(Trigger.isInsert && Trigger.isAfter){
        handler.OnAfterInsert(Trigger.new);
    }
    /* Before Update */
    else if(Trigger.isUpdate && Trigger.isBefore){
        handler.OnBeforeUpdate(Trigger.old, Trigger.new, Trigger.newMap);
    }
    /* After Update */
    else if(Trigger.isUpdate && Trigger.isAfter){
        handler.OnAfterUpdate(Trigger.old, Trigger.new, Trigger.newMap);
    }
    /* Before Delete */
    else if(Trigger.isDelete && Trigger.isBefore){
        handler.OnBeforeDelete(Trigger.old, Trigger.oldMap);
    }
    /* After Delete */
    else if(Trigger.isDelete && Trigger.isAfter){
        handler.OnAfterDelete(Trigger.old, Trigger.oldMap);
    }

    /* After Undelete */
    else if(Trigger.isUnDelete){
        handler.OnUndelete(Trigger.new);
    }

}

Example Trigger Handler Class

The Apex Trigger template above calls a handler class to execute the trigger logic, the trigger handler class should be defined as follows:

public with sharing class ObjectTriggerHandler {

    private boolean m_isExecuting = false;

    public ObjectTriggerHandler(boolean isExecuting){
        m_isExecuting = isExecuting;
    }

    public void OnBeforeInsert(Object[] newObjects){
        // EXECUTE BEFORE INSERT LOGIC
    }

    public void OnAfterInsert(Object[] newObjects){
        // EXECUTE AFTER INSERT LOGIC
    }

    public void OnBeforeUpdate(Object[] oldObjects, Object[] updatedObjects, MapObjectMap){
        // BEFORE UPDATE LOGIC
    }

    public void OnAfterUpdate(Object[] oldObjects, Object[] updatedObjects, MapObjectMap){
        // AFTER UPDATE LOGIC
    }

    public void OnBeforeDelete(Object[] ObjectsToDelete, MapObjectMap){
        // BEFORE DELETE LOGIC
    }

    public void OnAfterDelete(Object[] deletedObjects, MapObjectMap){
        // AFTER DELETE LOGIC
    }

    public void OnUndelete(Object[] restoredObjects){
        // AFTER UNDELETE LOGIC
    }

    public boolean IsTriggerContext{
        get{ return m_isExecuting;}
    }
}

source:  http://macscloud.com/salesforce-apex-triggers-the-definitive-guide/

Hope this helps :-)