If you booked a specific cabin, you won't be upgraded. If you want an upgrade, ask upir TA you will pay for it.
There are no tips for free upgrades. Free upgrades only happen for 'guaranteed' room assignments if the ship wants to book more rooms in the class you picked, or for booking problems or general customer service problems.
I consider upgrades to be a gift. If you get one that's great, a nice little perk to your cruise. Always book the cabin catagory you want that way you won't be dissapointed if you do not get an upgrade. If you truly want an upgrade you can ask your TA -if available you will have to pay the difference between your current cabin and the upgraded cabin. Never book a lower cabin catagory than what you want in hope of an upgrade imho.