I have a feeling if you need to ask that on a train sim forum... Anyhow for starters you need to be a steady, reliable person particularly when unforseen situations arise. Able to understand and remember operating Rules and Regulations, commit to memory for route knowledge and signalling on lines you might work over (no HUD in the real world). Solve minor technical issues with the train yourself. Be prepared to work long hours largely isolated from other people (train cab is nearly as secure an environment as aircraft flight deck these days), with some very odd shift start times. You need to be able to pass a fairly strict aptitude test and medical requirements which include near perfect vision in both eyes (I think glasses might be permitted these days) and the reason why I was unable to consider a job in the traction grades as I have a lazy left eye. You also absolutely must be drug free, not just illegal stuff like weed, cocaine or worse but also some prescription and non prescription medicines which can induce mind altering tendencies, such as codeine or the ingredients in "drowsy" anti histamines, cold and cough remedies.
I’m pretty sure you have to live within 1 hour drive of where they are based at also, that’s what I’ve read before about train jobs anyhows. I’m not sure what they would think about if that hour is public transport rather than personal car though. I live within 1 hours drive of Newcastle Central by public transport also, that public transport system is on strike currently for up to 12 weeks, i imagine if I worked their I would be having some difficulty right now. edit: seen as this thread is tagged TSW4 I should add if you want it become an LNER driver, they’re is ECML Doncaster to Peterborough available
You also need some railway experience. At least for my metro, there is no direct way to apply to be a driver. You need to move up the ranks, gain experience and then you could talk to your manager to move forward to be a driver.
If this is a serious question I would highly advise you got to the website and sign up to job alerts/ have a look at what's there currently (I believe there are a couple of onboard catering/customer service jobs going at the moment) and just get some experience on the railway. Then if you enjoy that and do well you can move to a train manager and then when the chance comes up move to driver. As Vern outlines though it's not as glamourous as it sounds and there are a lot of tests and medical stuff you'll have to go through and then again as Vern says you can't be on any sort of drugs or even alcohol as if either of these things are found in your system when you signed on for work, you'll be looking for a job elsewhere. Another thing that hits a lot of people hard is when you have to stay over, for example I actually haven't been to my proper house for two nights, one night in a hotel and then tonight in a flat I have near London so if you have a partner they need to be aware of this as it may effect them as well, though my mrs seems more disappointed when she finds out I am not staying over! There are loads more things I can list but I have just looked at the clock and so must whizz through my alerts and get some kip before work tomorrow! It's the best job in the world, but you must always be prepared for the worst case scenario as so many factors of the job rely on others.
And the other very important point to remember, at no stage of the selection and interview process give the impression you are a rabid train enthusiast or sit in front of the PC or console playing train games. Most railway managers (even though in my experience many were Uber cranks themselves) tended to take a dim view of overt enthusiasm. Whether that was fear of distraction when doing the job or the fact you’re not really there for the right reason, I was always told keep it low key if even mention at all. So when I applied for a job in the Diagramming Section at Paddington in 1983, sat in front of the interview panel headed by Alan Sweetnam (aka the Colonel with his great handlebar moustache and fierce some reputation but actually a great guy), I placed great emphasis on the logistics side of the job, not getting my hands on the Western loco and train crew workings! And I got the job which then later led on to a move into the Control where I spent the rest of my railway career, under various guises and companies finishing up with Network Rail. The railway is, generally, a good place to work if you fit in and keep your nose clean. And certainly for my generation with the addition of BRASS it has provided a very nice occupational pension which meant I could retire at 57 (and 5 years since have flown by!). But as Matt says above, be flexible and prepared to start out in a job or with a company that might not be your first choice. I worked with people in the Control who went on to become drivers or guards and equally the other way, drivers, guards or even signallers who decided to move into the Control where we had a wealth of experience from all sides of the railway family (and despite the at times lousy top management, it really was a bit like a family).