1. Watch TV shows in Finnish (with only Finnish subtitles) and understand the storyline.
2. Order in shops and restaurants (and when the waiter tries to uses English politely explain you want to practice your Finnish).
3. Introduce yourself to new people and explain why you are studying Finnish and how long you have been studying.
4. Understand when you hear a phrase that is the same in your language used in Finnish
For example you hear someone say "elää kädestä suuhun" and straightaway realise it must be "to live from hand to mouth".
5. You can read and understand signposts, shops ads and those cheesy sayings they put outside coffee shops.
6. You instinctively know how to "invent" words in Finnish based on the equivalent English word. You already know the word "fuusioida" ("to fuse"), so then you when you want to say "to visualise" you suddenly find yourself naturally saying "visualisoida". Warning: don't over use this! At least in my opinion it's nicer to use the real Finnish word if you know it.
7. You (occasionally) find yourself saying a word in Finnish, and you don't remember where you learnt it from, and you aren't even sure what the equivalent word is in English.
8. You have a had dream in Finnish (or if you are me, more likely you've had a dream about learning Finnish and at least one or two Finnish words were in there).
9. One the rare occasion you find a Finn person that speaks no English, your skills are finally essential and important - because you can communicate in Finnish.
10. When you ask a Finn "Puhutko sinä englantia?" (Do you speak English) and they reply "Vähän" (A little) you find yourself continuing in Finnish, because ... I mean they only speak a little English. (P.S. they always say a little).