I don't have swelling problems yet. In my last pregnancy, I tried to lift up the legs and feets at home during night time. I always do very gentle simple upward movement massage on leg before I sleep.
You can try to do some simple exercise, eg. moving/turning around the feet or ankle area.
really depends on people. For me, I am those kind of people who only got little swelling problem even taking long hrs of aeroplane. In my last pregnancy, my ankles only swell a bit one wk before giving birth.
But, I do know some people who got swelling problem easily even non-pregnant.
Although I am still ok now, but will keep on doing simple massage and exercise for prevention.