I find myself saying phrases in a non-native language that are ambiguous, and often get understood differently from what I meant to say. This can result in what I say being interpreted as the exact opposite of what I mean. I suspect that being a non-native speaker means I'm not as in-tune to the way things are expressed, so my faults in expression give strength to misinterpretations. Sometimes this is similar to how an English learner's "I can/can't do it" might be ambiguous, due to their pronunciation.
How can I practice avoiding ambiguity in conversations, so that I'm better understood?