Warning! The SOL cache series expose the geocacher to excessive UV radiation in an environment where it feels comfortably cool. Do not get a sunburnt, since it raises the risk of skin cancer significantly. There's nowadays also mites in the Helsinki archipelago that are contaminated with the TBE virus. The proper means to hedge against the disease (Kumlingen tauti in finnish) is the vaccination.
You need a boat to get in here. Most likely, if you're walking through the whole series you may want to take something to drink and eat along.
The boat key is available from the library of Laajasalo (N60°10.735' E25°03.319') against a deposit of 20 euros. The library is open from 29th May to 29th August on mondays 10-20, tuesdays and wednesdays 13-20, thursdays to fridays 10-15. The phone number to the library is (09) 3108 5084. When you use the boat, you'll need to lock it properly on the both sides of the beach (N60°10.807' E25°04.121'). Don't forget to thread the cable through the eyelets of the scull too!
Alternatively you can use M/S Maria from 18th June to 22th August 2004.
Bring at least a fully recharged mobile phone and something to drink. Even if you don't want to spend more time than neccessary on the island, you'll probably get thirsty. Hint: the SOL5 grounds is a perfect place to have a snack too.
Don't worry about the exhange items. The default is that there are only travelbugs in here. If you feel like it, you may write as much as you want on the log books. In that case it would be nice if you sharpened the pencils after using those with your own pencil-sharpener (there isn't one in the containers). Or just use you own pen.
Follow the nature trail (Luontopolku in finnish). It's marked with arrows and tiny red sticks on the ground. The first cache is easy, perhaps even far too visible. If you can, you may camouflage it better.
If you like, you can log your visit with your WAP phone at http://rtr.ca/geo so you don't need to care about logging later.