Marchmona, those are actually some really good questions. I have been living in Sierra Nevada for a few years now and writing in my "annual post" about the piste conditions but the information for first timers always get spread out as I answer questions. I will try to put most of it here in this reply and if you have any more questions please don't hesitate to ask again!
The first thing to do if you are looking at going to Sierra is to check the
weather, for that I recommend the following sites:
http://www.cetursa.es/En%20pista/Meteorología where you can see about 4 days ahead (but in Spanish) and on the right of that page you have webcams and pisteplan etc
and
http://www.snow-forecast.com/resorts/Si ... a/6day/mid which is pretty selfexplanatory
I have to point out that they aren't always right, less so the further ahead that you look, so a small pinch of salt is required.
Cadenas (snowchains), now there is a tricky area...
You can buy them at the bottom of the mountain at the last petrol station just before you start your ascent and then there are a couple of places on the way that have signs offering them as well.
Do you need them... Well last year YES! (but then again last year was nuts with snow:crazy:) as a matter of fact there were a few times when Guardia Civil wouldn't let you up without them.
Saying that I should point out that 1. it was the only time I ever saw that and 2. I have a 4x4 with offroad/winter tyres and I was fine without them. I think they let me past since they saw my tyres and I said I am Swedish and born in the snow "this is nothing"
My answer is: if you have a 4x4 or if you have driven in snow before (like me) then in general you don't, and I will try to update here if that changes due to snow conditions. If the signs at the bottom say you do please look at what kilometre because it seems like many times they put that up for if you are going to drive at the top of the mountain
Also it is worth mentioning that the plough machines go through at least twice/day when snow is heavy.
Skilessons There are lots and lots of teachers and many schools on offer in Sierra. They teach all languages and all levels. As a matter of fact for a beginner the Sierra Nevada is ideal since it is more geared to them and intermediates. Certain schools also have teachers specialised in teaching handicapped students should anyone need that. If you want any recommendations send me a pm with what you are looking for and I will point you in the right direction.
Clothing the Sierra is a strange place when it comes to weather... It can be boiling warm but once those winds set in it is icy cold. So, my advice is to “dress like an onion”. Layer upon layer! Always always bring a hat (kids HAVE TO wear helmet, which you can rent) and you must have gloves!! Apart from that get some good factor 30 (or 50) sunscreen. Obviously winterclothes/skiclothes are what you need but if you are only coming for the day think waterproofs with LOTS of layers underneath. You can also rent clothes up there I believe and I have seen a sign on the road up that rent too.
Equipment please make sure you rent from a reputable shop and also that you rent IN Sierra Nevada. You have no idea how many people rent at the bottom or on the way and then when it comes to skiing or snowboarding find that there is a problem with their kit and no-one to fix it. I tend to recommend Rio Sport just by the telecabina Al-Andaluz, they have great equipment and service and speak perfect English if need be.
As PS I would like to add that if you can stay away during weekends or absolutely peaktime DO so, the lines for the chairlifts etc can be horrendous at those times
. The snow conditions are good for what there is and if you are a complete beginner it is worth it to go up and have a try. 
. Keep us informed.
) people use the web site. It would be great if they had an english page.
. It doesn't matter that you "couldn't see the lign/sign/whatever" it doesn't matter that you were snowed in and couldn't move nothing matters....
There is snow but not as much as we would want or would expect... and it is WINDY...
for a few days) but from what I hear the prognosis for the next few days isn't great. 
and 
