Establish the purpose behind the characters' interaction. Determine if they're meeting to trade goods, settle differences or just to say 'Hello.' Establish the tone of the scene by explaining the characters' motives.
Determine the setting. A dark forest, for example, may require somber dialogue. A crowded campsite may inspire more lively interaction between the characters.
Keep in mind the historical and social context of French-Native relations. Emphasize the language barrier that existed between the French and Native Americans. The dialogue should be cautious also -- highlighting the tense relations between the two parties.
Emphasize relevant French and Native words. Research both languages to learn how to translate "fur," "trade," "beaver," and other relevant terms. Translate these words into the speaker's native language to give the dialogue authenticity.
Include descriptions of actions. A language barrier may require greater emphasis on physical gestures and body language from the characters. These actions will demonstrate the relationship between the characters.