At our airline in Canada, our SOPs had us flash the seat belt signs twice through 10,000' then as a last warning, we hit the "chime" button twice when the landing gear is selected down (as if landing gear weren't a good enough indicator). As an added thing, you can get your pilots to give the estimated time to touchdown during their announcements.
For takeoff, the purser (or whatever they are called these days) will call up the flight deck and tell us that they are secure. As a final warning, I have done either double chime them or make an announcement, "flight attendants please be seated for takeoff" just before taxi onto the runway.
Hope that helps.