Everyone has to start somewhere and no you're not likely to be some kind of snowboard god from day one. What you should do though is get some lessons and no we're not talking lessons from someone you know who already snowboards; they won't be trained to teach and you are very likely to pick up bad technique that could haunt you for years!
So starting means getting lessons which really, which then comes down to two options; home or abroad? With the proliferation of indoor domes with 'real' snow, learning in the UK has become much more common place, but the choice is yours, below are listed some of the pros and cons.
Back when I learnt snowboarding indoor domes were not an option (Tamworth Snowdome was closed for refurbishment at the time and the others did not exist), learning on real snow in England was not an option. Now however there are a whole number of snowdomes scattered across the UK.
The standard of lessons at the indoor domes is very good; these are now well established businesses with professional instructors. It's not that cheap mind. Typically you will need to reach a standard where you can link turns, dna this will take a number of lessons to achieve. An hours lesson will be in the region of £30 and as such it is likely to cost you in the region of £150 before you can ride on the slope by yourself. If this doesn't seem too expensive, or your only intention is to ride indoors for a while then get booking! Don't leave it too late before booking as the domes do get booked up very quickly as winter approaches.
If your nearest snowdome is too far for you to get to, or you fancy saving a few pounds then you could try a dryslope. As I have never visited a dryslope I can't comment too much on this option other than to say that people I know who have riden a dryslope say the experience and the feeling you get from the board is definitely different.
However you go about learning (and an indoor slopes is possibly the most common and sensible method), it may well be useful to get lessons in resort too. So even if you're determined to learn in the UK do have a read of the next section too.
If you fancy jumping in at the deep end then why not learn in resort? It's what I did! A mountain is without doubt a different beast to an indoor slope, so there are advantages to doing this. The obvious disadvantage is that if you decide boarding is not for you (are you mental?!) then you are stuck in resort. However as long as you pick your resort well there are always plenty of other things to do (like drinking!).
Regardless as to whether you have got to 'linking turns' level indoors or are a complete newbie it is worth checking what deals are available at what resorts. In some you may find that getting a package deal of lessons, liftpass and snowboard hire is actually cheaper than just liftpass and hire! It's really a non brainer in such cases; sign up for lessons regardless (you can always drop out if you want). You will never stop learning thouhg so my advice is the more lessons the better, especially in the formative years.
Where to go for your first snow trip abroad should also be something you consider. In general there is little point in going to one of the big name resorts with a mass of terrain for your first couple of trips; you simply won't make use of it so save some money and head to a smaller resort. Andorra is a traditional favourite, Bulgaria is also worth looking at but there are smaller resorts in Italy and Austria too. France is probably the best known European destination but it may not be the best destination for your first trip; the instructors (ESF) are a mixed quality of snowboard instruction and I have heard of people in tears! Switzerland is another well known alpine country but prices are generally high.
If you are learning indoors then most of the equipment will be provided for you but you will need some suitable gloves and trousers. The trousers (or pants as they seem to annoyingly be being called with increasing frequency) can often be hired.
When it comes to heading to a real mountain the best bet is to hire your boots, board and bindings first time around, you will want several pairs of good thick socks, waterproof trousers and jacket (the jacket can often be worn off the slopes; which somewhat mitigates the expense), goggles (much better than sunglasses) and some warm hats (most people also wear a helmet these days but you can probably hire that).