There are some simple rules to follow:
1. Booking three months in advance gets the cheapest fares
2. Always check the cost of two singles rather than just a return
3. Don’t assume First Class will be more expensive than Standard
4. If using more than one train company on a journey check the separate fares for each part of the journey
5. Cheap advanced tickets will normally be for designated trains, if you are not sure which train you will be travelling on book the more expensive open tickets
6. Normally cheap advanced tickets are not refundable but can usually be moved to a different day/time for a £10 charge depending upon availability
I normally book all my tickets through one Train Company – I use Virgin as I find them reasonable to deal with and their web site easy to use.
As an example, I’ve just checked
www.virgintrains.co.uk for a journey from Lancaster to Edinburgh on the 17th March after 8:00am returning 19th March after 18:00pm.
The cheapest Standard off-peak return fare travelling up on the 8:40am train and back on the 18:11pm is £47.60. The cheapest single fares are £12.50 going and £7.00 coming back. The £12.50 is for a First Class ticket which is £1.50 cheaper that the £14.00 Standard ticket and that’s a discount of £100 off the normal Open First Class fare.
Hope this helps.