I will usually just toss and turn or get up and turn off the alarm and get my day going earlier.
That depends: reading, on-line surfing, crosswords, writing, etc., or just having something to drink, i.e. water, some tea, a juice, and, sometimes, a little treat (to eat) and then returning to bed.
It's so quiet where I live that it's easy to sleep whenever you want. After all the years in the Marines? You learn to grab any sleep you can whenever you can.