On this topic, it's been pretty straightforward for me. I asked before committing to a purchase whether the ticket was eligible for FF credit. I suppose if the answer is yes it would be good to get it in writing including by e-mail. I've had one ticket with a bright sticker on it saying Not eligible, in which case I didn't try. In other cases, including when I didn't ask about eligibility, I didn't have a seat assignment at the time of ticketing, so I called the airline directly to get seat assignments, gave my FF number at the same time, and it worked out.

Andrew Missouri