I was a compulsive record-keeper during my early teenage years, recording my sightings not just in my nature journals and sketchbooks, but also with charts and field trip reports. There's nothing of scientific value in these records; I didn't maintain them long enough to be able to see any trends. But I took them very seriously, and felt I had a sort of scientific duty to write all this stuff down. In any case, it was good training and helped me hone my observational skills.
Bird Data: I kept records on my notable bird sightings from 1971-1974 (when I was 12-15 years old)
Broadwing Hawk Data: Although I was once smugly assured by a know-it-all hawkwatcher that "broadwing hawks don't summer south of Canada," these small buteos were a frequent sight and sound during spring, summer, and early fall when I was growing up in southern New York State.
Wildflower Data: I wrote down the blooming dates of wildflowers from 1973-74.
Morning Notes: During the summer of 1973, I got up early on four occasions to write down the order in which birds began singing.
Field Trip Notes: I occasionally kept data sheets on my sightings during trips to Brinton Brook Sanctuary.