If I think I know the word for a concept or whatever I am trying to say, I will spend a little bit of time looking for it. However, I rarely have all the words that I would need to express myself the way I do in English, so I just open my mouth and try to let the conversation flow and, if need be, describe the word instead. Sometimes, I just use a modified version of the English word. I find people do this all the time in Finnish (particularly youngish natives).