You don't need Finnish to visit — everyone speaks English. But a few phrases earn goodwill.
Hei (hello, casual). Moi (hi, even more casual). Näkemiin (goodbye, formal). Moi moi (bye, casual). Heippa (bye, friendly).
Kiitos (thank you — the most important word). Kiitos paljon (thank you very much). There's no direct "please" in Finnish — tone and context carry it.
Anteeksi — sorry / excuse me. Kyllä — yes. Ei — no. Puhutko englantia? — Do you speak English? (Answer will usually be "yes").
Pöytä kahdelle, kiitos — table for two, please. Lasku, kiitos — the bill, please. Terveydeksi — cheers (literally "to health", used after sneezing too).
Yksi, kaksi, kolme, neljä, viisi, kuusi, seitsemän, kahdeksan, yhdeksän, kymmenen.
Hei hei (bye). Ole hyvä (you're welcome / here you go). Hyvää päivänjatkoa (have a good rest of your day — when leaving a shop).
Common mistake
Trying to speak Swedish instead of Finnish — only about 5 % of Finns speak Swedish as first language, and most Finns prefer English to broken Swedish.
Good to know
Finns understand that Finnish is hard. Any attempt is appreciated; no-one will judge your pronunciation.