For Corfiots, a meal is a social occasion and accordingly, food is ordered for the "table", not for the individuals. You order a bit of everything, spread it around the table, or more often cover the table with different dishes and everybody picks at everything. If or when more food is needed, more is ordered. There is also quite an element of status involved in the ordering and it is not uncommon for Greeks to order far too much, either to show off their status or to show their generosity. This unfortunately leads to a fair amount of food being wasted.
You can of course stick to the Western habit of not sharing food but order for each person,. Greek people are used to foreigners and their habits, but you will miss out on an enhanced eating experience. It's very common to order a number of appetisers for the table and you main course individually.
Use of the fingers instead of forks and knives is very common. After all, food is there to be touched and eaten, not picked at. Eating meat (especially lamb, chicken or fish with a fork and knife is considered a little silly because you are missing out on the most sensual part of the experience. Bread is used with the meal to push the food on the fork and to soak the oily liquids that remain from the food.