Where to start? Probably March 1967 when some other boys persuaded me to start trainspotting. I lived in Cross Gates, Leeds, and we would turn up at Leeds City station one weekday evening for a couple of hours, homework permitting! On Friday we would gather at Cross Gates to see the steam-hauled Manchester-York and on Saturday we would bunk Holbeck shed then hang about on the "triangle" near the West end of Leeds City where we could see everything passing on the avoiding line. Soon we took a Saturday trip to York (still some dumped steam there) then since I got back OK we followed it up with Doncaster and Wakefield and, the biggest trip so far, Manchester during the summer holidays where the number of active steam sheds and the variety of electric locos was amazing.
Somewhere along the line came the idea to see every class of loco, then every member of every class, and you know where that leads! Train fares were much cheaper then, especially for a young teen paying half fare, and the borders for a Saturday day out by rail were maybe Newcastle, Carlisle, Hull, Grimsby, Crewe, Derby, Liverpool and (at a pinch) Birmingham. A few sheds such as Westhouses and Blyth Cambois were really awkward to reach, and a couple of us decided to branch out and go with railfans clubs coach journeys to the difficult and faraway places. Eventually, a couple of years down the line, when I was about 15 my parents let me go to London in the company of a couple of older boys for a weekend shed bash. Of course, for the self-organised trips we didn't have any permits so just sneaked round everywhere, almost always successfully. I remember just once we balked at a shed bash, and that was to "do" Stewarts Lane by means of crossing four third rail tracks with trains coming every few seconds, in view of a signal box. Though I remember with the Dalescroft/Jubilee club forty lads crossing a live third rail track at Selhurst, and the lot of us veering off the M1 in our coach to do an unscheduled bunk of Tinsley on the way home from a Midlands trip!
I don't think my own sons did anything more adventurous than going to Altincham ice rink, and the way things have gone I certainly wouldn't have encouraged trainspotting, at least in the old way!
When we were a bit older (16/17) we bought a Freedom Of Scotland pass and, together with a planned club trip to Glasgow Works, we tried to see every single loco in Scotland! This involved multiple overnight journeys, the odd hotel and bashing every single shed except Fort William, often several times. I came back "needing" just seven locos which was upped to eight when 20007 was transferred from nearby Tinsley to Haymarket! And that was a sign to give up and become more interested in music and girls.