The great thing with the railways is that pretty much anything can turn up. Freights are rather good, you have operators such as Freightliner, DB Schenker, Direct Rail Services and GBRf around the north east primarily. I personally prefer lineside shots rather than station shots (excepting some places such as Doncaster for the fast lines).

Regarding 'how' to take a train shot is very similar to buses. Just make sure your exposure is ok along with a good shutter speed to 'stop' the train (General rule of thumb is 1/100 for every 10mph - if you were on a 125mph line you'd want a shutter speed of 1/1250. Linespeed of 60mph and ideally 1/800 but 1/640 would do too).

I typically try to get the front of the train and as much of the side as possible. Not a huge fan of rear shots but, if it turns out right, it can be great.
http://www.realtimetrains.co.uk/search/advanced Realtime Trains (RTT) is an absolute gem. Say if you were at Durham station and wanted to see what was due next, just search 'Durham' in the top left search box and hit go. There are various other filters/options on there too.

If you're wanting to look at other pics, please feel free to have a look at my photostream.
Feel free to give me a PM if you've got any questions!

(If you're interested, on Wed or Thu this week there should be a DCR locomotive hauling a preserved British Rail ScotRail liveried Class 47 (47712) from Bishop Auckland to Carlisle for the upcoming open day at DRS' Kingmoor Depot [which anyone is very free to come along to, I'll be there]).