As a general rule, I'd say that if you are often left outside of a conversation or even get frown upon for trying to participate it is probably because they don't deserve your company, quite seriously. You may also think you are incompatible. It is their fault, not yours (at least more so than yours in most cases), pick people with whom you can have conversations (meaningful or not). As a temporary solution, try to just listen to them, and try to speak when there are fewer people, maybe only one. It can help to gather some experience with them. Sometimes it is just not appropriate to participate in a conversation. It could be a situation where politics apply (sucking up to the boss is a common example). Don't get involved in such activities, they are BS.
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Another non-English speaking - DX'd at age 38
"Aut viam inveniam aut faciam." (Hannibal) - Latin for "I'll either find a way or make one."