Stanley or hobby knife: Get a good quality knife in metal. Those plastic ones keep breaking apart and you rish cutting yourself to death in the process. Also keep a good stock of replacement blades. Allway use fresh sharp blades: You don't need to use as much force to make the cut thus minimizing the risk of the knife slipping. (Also if you DO cut yourself a nice clean cut will heal faster...) I know that there's a lot of advice saying that you should allways point the knife away from yourself. While it is basically true I do find it easier and more controlled to cut towards my thumb. It costs you some cuts every now and then so be warned and do it at your own risk.

Cutters: A nice sharp pair of cutters are essential for removing stuff from spures, cutting metal, plastic, fingers and anything your heart desires. You can get a nice and cheap pair of cutters from most hardware stores so don't bother with the GW stuff.

Fine toothed saw: For heavy cutting in plastic, wood or metal.

Superglue: Don't leave home without it! Usefull for most assembly situations. Superglue will glue metal, plastic, wood, rocks and fingers with equal ease. Apply a bit of superglue to the joint. Hold the pieces together for 10 seconds or so. This is usually enought to keep the parts together. However the glue doesn't reach full strength untill after a couple of hours. To speed up the bonding process try breathing on the joint. Water acts as a catalyst for cyanoacrylate (Which is also the reason why it dries so darn fast on your fingers...).

To get a good bond you need an even surface where the two parts meet. When that isn't possible you can use a small blob of Green Stuff covered with superglue to produce a good bonding area. You need to leave it to dry overnight for maximum durability though.

When working with Green Stuff you should work in many stages allowing each stange to dry overnight before continuing work. If you build up too much at one time there's a good chance you accidentally ruin it with your fingers. Also more complex shapes are achievable if you work gradually and methodically. However as with all skills practice makes perfect so don't wory if your first attempts look awfull.

To manipulate Green Stuff nothing beats a couple of needles of varying thickness, a razor blade and a good hobby knife. A little tip if you are having trouble with your fine details of green stuff coming off: Try applying a very small ammount of superglue to the blob. This will instantly harden part of the GS and attatch it to the miniature making it easier to sculpt with the rest of the GS.

Read Drassanar's article in Incoming #22 for an extensive guide to sculpting explained much better than I ever could.

Brushes and stuff.

Do yourself the favour of getting some decent brushes. If you can spend money on miniatures you'll also want some good brushes to paint them with.
I use "Raphael" brushes by Kaerell. These brushes have fairly stiff bristles which is essential for delivering the paint precisely where you want. I think they are originally designed for use with laquer or varnish work so they've got very fine bristles as well which is excellent for delivering a smooth coat of paint.

I do the majority of my painting using a size 2 pointy brush. Apart from that it is a good idea to have a fairly large flat brush for drybrushing and a medium size brush for basecoating larger surfaces.
Of course you'll also need some fine detail brushes but i really don't use them that much. The big problem is that paint can sometimes dry before it even leaves the brush. With a steady hand you can get almost as good a result with a size 2 with a good pointy tip.

I also got myself an airbrush but frankly i don't use it very much. It is usefull for painting stuff like BFG planets or rivers where it can produce some nice smooth colour transitions. You can also use it as a more eco friendly alternative to spray cans. However you can definitely do without one just as well.