Welcome to cruise-chat. Let me see if I can help with some of the questions:
1)What is normal tipping policy on a cruise?
--Gratuities are distributed at the end of the cruise and may be charged to your onboard charge account if you wish. Suggested gratuities: waiter - $3.50, asst. waiter $2.00,
asst maitre d' $.75 / stateroom attendant (concierge class) $4.00 - these are per person per day. Tips for bar service are already included in the price so no additional tip is expected.
2)If we decide to skip the regular dinning room for dinner is there an additional charge? Same goes for room service (if even offered)?
There is no additional charge for eating at the alternative casual dining room (buffet area) or for room service (available 24/7). You may wish to tip the server who brings you room service however.
3)Charge for sodas and water or only booze?
They do charge additional for sodas and bottled water.
5)Do you have to pay for shore excursions or are there shuttles provided to see the towns on your own?
shore excursions incur additional costs. However, on that Century itinerary - there are a number of ports that offer complimentary shuttle service into the center of town - but then you are on your own for touring.
6)What is the best way to cover currency exchanges since some of the port cities do not use the Euro? (i.e. go to a bank ahead of time to get money specific currency, use the exchange on board, atm machines in specific cities)
I always suggest ATM's as the best way to handle the money situation, but again on that itineray we did get some currency exchanged at the onboard bank as a convenience.
I wrote a mega-review of my Baltic cruise last year on the Century (as did Tom Ogg) that might shed some light on many of the questions and concerns you have: