It's not quite that simple: if you are a number-cruncher (I think the train ones are called gricers, or used to be) then it's not so easy to know exactly which Class 78 will be pulling the coal train to Drax on a particular date. You can get so far with random visits but eventually you need to start hunting individual locos or EMUs down, and that takes intel....
Aircraft-wise I still don't have digital photos of eleven of the RAF's Chinooks: ZA674, ZA675, ZA679, ZA682, ZA707 (all original buy, from circa 1980); ZD980, ZH775, ZH895 and the recent ones ZK557, ZK558 and ZK563. And they are all based at either Odiham, down the road from me, or Benson, less than an hour away by road.
Conversely when I wanted to photograph the three British Airways retro-scheme 747s, I hunted them down coming into/departing Heathrow using Flightradar 24 to determine when they were arriving/departing and ADS-B Exchange to ascertain, close to the time, which runway was in use in order to position myself appropriately.
Sometimes twitching looks easy....
John