Before leaving for the station ensure you have your money/tickets with you. It may be helpful to know where you are going, why not check National Rail to find out.
Once at the station head towards the ticket machines, or the booths. If you have a ticket/Oyster card head to the platform. When the queue is large it can be helpful to pay by cash rather than selfishly using a card to pay and holding everyone up. As you move away don't block others when staring stupidly at the screen showing which platform to go to. Move to the side.
When heading towards a platform... KNOW YOUR SPEED. If you are slow, or just stupid, walk close to the side (signs will tell you which side to stick to, but as a rule keep to the left) that way more speedy people can get past you. Is that your mobile phone ringing? Learn the skill of answering and walking... it's far better than stopping and blocking the way of everyone else. Did you know it's possible to talk and walk? Weird. Bear this in mind if transferring between trains as well.
Trains have doors. These can be opened usually by pressing a button (some do have handles). These buttons are generally round, and surrounded by flashing lights when operable. Apply pressure using a digit (these are located on your hand). VOILA! The door will open. Isn't that better than standing there like a lemon blocking the way of the guy behind you?
Allow people off the train first. Strangely walking into people moving in the other direction will impede your progress. Allowing them to pass will mean everyone gets on the train quicker. If a seat is free take it, if not move to the centre or the ends of the carriage as far as you can go. I know it's tempting to stand near the door, however for some reason no one has yet developed the ability to walk through you.
If the train is particularly busy, and you are getting to know your fellow passengers rather too well, keep your quips to yourself. I'm sure "It's like a tin of sardines in here" was funny in your head, but it's not going to cheer anyone else. Reading a newspaper in this situation is also not advisable, unless you do wish to be punched in the face.
Don't stare and when talking with someone else try to avoid involving the whole carriage in your conversation... talk at a normal level, your ears still work on a train.
When leaving the train do so quickly and don't stop as soon as your feet touch the platform, often other people will wish to get off the train behind you. Why not move away from the train before you ponder your new surroundings.
Have your tickets ready... barriers are so much easier to get past with a ticket ready, it's really dumb to wait till you are at the barriers before finding that ticket.
Leave the station... you have reached your destination.