And idea may spring from a memetic change. But ideas are not memes. I haven't the knowledge to speak to. I would say memes are a subset of the ideas, with special properties like transmissivity, reproductivity and such things. A meme doesn't necessarily have to work on a conscious level, although many does since we communicate so efficiently on that level.
Different memes can spread differently in different mediums.
Its a bit like different ecological niches or disease vectors, different organisms have specific preferences. It may or may not be expressible as a change of behavior, communication or in other ways. I agree with Anders on most points. However I would like to add some remarks with regard to the notion of 'operation at a conscious level'. The distinction conscious-subconscious is no longer valid in its original form.