There is quite a variety of ways you are expected to moore in the marinas in the Baltic sea. To list the main one, by order of frequency:
Steps 1 to 5 below are describe with bow to the pier. However, it is usually easier to get in backwards if the boat has a bow thruster, aft to the pier, keeping the rudder fixed and using the bow thruster for direction.
This is the sign pole that indicates that you are entering a marina or a guest harbours. The signs are placed on the pier devoted for visitors. On some marinas, no places are reserved for visitors. Visitors can just occupy berths not indicated as "Reserved". In some other, there is a green sign for free places and a red one for the reserved berths.
This is the exception, usually outside of the peak of the summer season
This is the most common setting as it allows for mooring a maximum number of boats.
Steps are as follows:
Mooring on a pendille, the mediterranean term for a mooring line attached from the pier to a chain on the sea bottom of the harbour, which acts as a secure aft anchor. Sandhamn KSS marina for example is using pendilles for mooring.
In such harbours:
This is often available in Germany and Denmark. The main difficulty is to assess the width between the poles in relation with the boat width.
In such harbours:
Nothing specific in this situation. Do not hesitate to moor backwards.
This is not a common practice in the Baltic, even though in some places there is no questions that is has to be done, such as at the entrance of the Kiel canal or in specific small places such as Hävringe, Christiansø or Utklippan.
In any case, should you wish and need to moore along side, try to get a contact with the target boat to get consentment, and choose a boat bigger than yours!