Uniform, the one bit of cadet life which you're going to need whatever you're doing. Basically, if this doesn't look good, you're stuffed. A good uniform makes officers think you're good and determined. Or something like that. Generally, the smarter your uniform is, the more highly the officers will think of you.

What you've got
The standard-issue ATC/RAF No. 2 uniform consists of:
Dark blue working shirt
Light blue (Wedgewood) shirt
Trousers or skirt
Black tie
Jumper
Brassard
Belt
Beret
(Rank slides)

Shoes aren't included, because they make you buy your own. Because they're such a huge topic, info on them can be found here. Oh, girls also have to have black tights. Being 100% male, I have no idea what to do when it comes to keeping them in working order, except that holes in certain places can be appreciated...
(Sorry, sorry, it's only a joke!)

Shirt maintenance
Keep it ironed, especially the epaluettes (the straps over the shoulders your rank stripes sit on). Hang it up after wearing it unless you're going to wash it. To keep the creases down the arms, rub a little soap down the INSIDE of the crease. Then iron it. Don't ask me why this works, it just does. If you really don't want to go around smelling like a laundry, spray de-odourant on 'em before ironing. Not too much, otherwise they can catch fire rather amusingly (unless it's yours).

Trousers
The soap trick also works here. Because the trousers are made of such a godawful material to iron, you may need more soap than on the shirt. Of course, you can just leave them under a pile of bricks whenever you come home from wearing them. If you've got a pile of bricks in your bedroom, that is.

Tie
Keep it tied around your neck when you're supposed to. Don't sit on it. How are you supposed to tell somebody how to keep a tie in good condition?!? Iron it at any temperature you damn well please, burn marks don't show on black (!).

Jumper
Keep the epaluettes ironed flat, any D of E badges in roughly the right place and nobody really minds. Because it's so damn big, heavy and shapeless, ironing is pointless unles you've done something really dopey like use it for a seat cushion on a minibus trip or something.

Brassard
The least favourite bit of uniform. The squadron number must be 6mm from the top. If you can't be bothered to measure, just make sure the gap doesn't look very big and the badge is horizontal. The ATC ID flash is best off being sewn onto the sqn number flash BEFORE sewing them both on. These are the only two which will never move as long as you're in the ATC. Classification badges go underneath, ideally just touching the ATC flash. When you put up your First Class badge, make sure you've got it straight (ie. top and bottom points of the star on the same line) otherwise you'll look like an idiot on parade. All the other classification badges are dead easy, just sew 'em to the ATC flash. Your marksman's badges must be 11mm from the bottom of the brassard and central. To get the badge central, measure how wide it is, divide that by 2 and mark the middle point. Now find the middle line of your brassard (starting at the top) and put the point you marked on the marksman's badge on the line. That looked long and complex but it's quite easy, believe me. The only exception to this is if you get a Cadet 100 badge. Nobody on my sqn knows the measurements for that, so go somewhere else to find out.
By the way, in case you're interested to know why the brassard has that pointless button hole, it's because on the regular forces' combat uniform, they wear brassards. Of course, theirs are cut from camo-patterned cloth, rather than blue or denim-grey, depending on how lucky you were when the new brassards came in. The button hole is to make sure the brassard can stay on the jacket rather than falling off.

Belt
You can't really go wrong with this. As long as there's no smears on the buckle, you're OK. A little polish might seem like a good idea, but the buckles are lacquered. Once you've put polish on, that strips the lacquer off, which in turn means you're spending a lot longer making sure the buckle doesn't tarnish. Just stick to wiping it with a soft cloth.

Beret
Everybody looks stupid with a new one of these. To get a sea-cadet style look, get the cap-badge central in middle of the forehead and then pull the brim down towards the ears. Rotating it over the back of the head makes this look truly stupid (and funny). To shape your new friend, follow the instructions printed on the inside of the lining. It's amazing how many cadets don't bother doing this. Now, if dunking a lump of wool in cold water and then dumping it on top of your skull doesn't sound very appealing, here's what to do. Take a small pair of scissors, the smaller the better. Cut the lining out, going as close to the stitching on the brim as you can. Now put the beret on your head. Grip the right edge firmly with the fingers and tug down over the right ear. If necessary, hold the left brim with your other hand. You now have a perectly-shaped, hassle-free beret. To be on the safe side, it's a good idea to have 2 berets, keeping one for any situation where you might need to show the inside of your beret to quartermasters/officers.
The cap badge doesn't need any maintenance. Trying to polish it results in blobs of polish being left in the little nooks and crannies you're never going to get into. On night exercises, you actually want it dull as possible.

Rank slides
If you're an NCO, chances are you won't need this advice, but for interest's sake...
Stick your slides on your epaluettes and iron them with the epaluette. Result - neat, flat slides. Don't let the iron go too hot otherwise your mark of authority might end up looking black instead of silver and blue. DO NOT try putting soap on these to keep the edges sharp, they're too thin. Plus, if you're out in the rain they could actually start lathering up. There's not much risk of this unless you start fiddling with them, though. Ditto shirt creases, before you all start cursing me!

The British issue combat uniform is dead simple to keep in working order. Because it's cut in DPM (Disruptive Pattern Material, the official way of saying blotches of light brown, dark brown, green and dark green), creases don't show up very well. Basically, keep your trousers with a crease of sorts. It doesn't have to bee good so long as you can actually see it. The jacket requires a little ironing every now and again, but other than that, there's not much to say. Oh, if you've received a DPM shirt, that does need a bit more care and maintenance.
The degree of care your DPMs will need depends on what pattern it is. There are 3 different patterns on issue to cadet units, Soldier 84, Soldier 90 and Soldier 95. Soldier 84 kit stands out because it will almost certainly have faded. It also has shoulder-mounted epaluettes and small pockets. If you're a history buff, it's basically the same as the WW2-style battledress jacket, cut in DPM rather than khaki cloth. As the name suggests, it was made to the pattern specified in 1984, just before the Falklands War. Soldier 90 pattern kit has the larger pockets and and generally looks better as it won't have faded that much. 95-pattern kit is what's on current issue (though my sources tell me there's a new 2000-pattern out, which I have yet to see in cadet service). The S95 jacket has the one central epaluette in the middle of the chest, large pockets, and is bound to be in decent condition. Trousers across the range don't vary that much, except for pocket sizes. Your DPMs will almost certainly be too large for you, or seem that way. It's a military thing, don't take it personally. On hte inside of the jacket and the trousers, there will be strings hanging out from various places. Pull these until the jacket looks pulled-in around the waist and then tie them off. You might find sliding the tugged bits of cloth down the string inside the jacket/trousers helpful. DON'T CUT THEM OFF AFTERWARDS!. For trousers, make sure they're not going to fall down halfway through running or something. This tends to be rather embarrassing for either sex, although females may find this proves rather popular with the male cadets... Of course, if it doesn't, then you've got some hard thinking to do!

Well, there it is, the lazy man's guide to keeping your uniform looking good. Hope it's useful.