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The best way to increase the probability of an upgrade is by booking a catagory guarantee. You decide what the minimum cat. that you are willing to accept and book a guarantee for that catagory. For example, if you book a cat. C outside guarantee, you are guaranteed a cabin in that cat. or better. Most often, when I have done this, I have been upgraded, although never from an outside to a balcony, but it sometimes happens.
