Let’s get one thing straight, I am no expert or anything and there are many who can do this sort of thing better and have more experience in using styrene. But as people have asked who I have done certain things and some have asked in general terms how I go about making stuff I thought I would start this tutorial/guide thing.
I have no real plan about how I am going to do this, I will probably just add to it whenever I think of something, or better yet when someone asks me how I do something I’ll give an answer in here.
Now, to begin, a quick run down on some of the tools I think are essential in building in styrene:

We have:
Cutting boards, excellent surface to work on, allows you do cut without you ending up with a rough working surface afterwards.
A sharp knife (or two), with plenty of spare blades.
Steel rulers, the more the better. They measurements need to run from one end, not offset into the ruler.
Wet and dry sandpaper in various grades. Normal sandpaper will do but I find using wet and dry gives a better finish.
In addition to the sheets of wet and dry I also take a piece of flat wood and glue some of the sheet to each side (a different grade each side). Comes in handy.
Set of needle files.
Green Stuff (or an equivalent filler) and at least one sculpting tool.
Not shown is a good light source, something like a daylight bulb lamp is beneficial.
Polystyrene cement. In liquid form with a brush applicator and in the more recognisable thicker consistency.
A series of razor saws / jewellery saws and a mitre block.
Pin vice and an assortment of drill bits.
In the next picture are some items which I use regularly, they can be of great benefit but I wouldn’t consider them essential.

Chopper II, great for doing small parts accurately and very handy when you want duplicate pieces. It has it’s limitations though.
Bench hobby vice, go for a solid multi angle vice. Avoid any cheap plastic crap.
Hole punches of various sizes.
A more extensive range of sculpting tools and tweezers.
Superglue & 2 Part Epoxy glue.
Clippers, pliers etc.
Small hobby G clamps.
Micrometer/Vernier,
Lighter,
Circle Cutter,
Protractor
Additional mitre blocks.
More to follow...