I would go for the Combined Edition of platform 5, with loco's, units and coaching stock (check amazon or your local WH SMITHS or Waterstones, if not in they will order it for you) as someone suggested, that way the photo's will help you establish which class of loco's your looking at, if your going to spot loco's, units and coaches, I usually take a notebook and a dictaphone, you can always write up what's been recordeded on your dictaphone, when you have a quiet moment to yourself. I'd also suggest you get a decent pair of binoculars, especially if your going to marshalling yards or depots. all this and this is before you decide if your going to take up railway photography. Your Xmas wish list, could be almost written up for you.
The dictaphone will come in handy for taking the numbers from coaching stock and extremely busy stations, such as some of the London termini or a place like Clapham Junction, where units are whizzing by virtually every 30secs. A dictaphone will definitely come in handy if your going to take the numbers from freight wagons but as someone has already said, that'll probably be a bit daunting for someone new to this hobby, it's something I really have no interest in doing and I've been doing this on and off since 1978.
Depending on where you live, I'd suggest travelling to the nearest mainline staion to get your bearings, before you venture out to the likes of Doncaster, Carlisle, Warrington, Stafford and Tamworth.
Welcome to the fraternity, I hanker for the days when absolutely everything was a new line in the book.
Happy hunting mate/