I always seem to be rushing for the train, so having to queue at the ticket office is a nonstarter for me.
Luckily, I discovered thetrainline.com, a handy little site that enables me to buy tickets days, weeks or even months before I want to travel.
Best of all, I can get the ticket in digital form sent directly to my phone, meaning I save on paper and simple flash the code at anyone that needs to see it.
I have not found any great financial saving on buying my tickets this way, but that may be dependent on the route I am using. What it does offer is convenience, and one less thing to worry about when using the train.