Finnish passport requirements
You have lived 4 years in Finland
To get Finnish citizenship there is need to live sufficiently enough in Finland. Required period of living depends on your Residence permit status. For instance, after 4 years since the moment you get residence permit status A (self-employment or employment basis).
You have not committed crime
Finns taking public order very seriously, for this reason Finland considered as one of the safest countries in the world. Offences for which foreigner have been punished by petty fines do not absolutely prevent you from becoming a Finnish citizen.
You have means of support to live in Finland
You should have enough money to live in Finland. Thus, you and your family can be financially secured.
You have language skills in Finnish or Swedish
You may heard probably that Finnish is known as very hard language. Nonetheless knowledge of the language has nothing to do with language test. Finnish language exam is called YKI, it is divided into 4 parts: Speaking, Listening, Writing and Reading. To pass exam you don't even need to pass all 4 parts, instead you need only to pass only Reading and Speaking parts, that is enough for obtaining citizenship. Moreover, if you don't want to study Finnish, you can study Swedish instead.