I found my brain spewing info about clay/sculpting and such and thought it’d be a good post here since other people might benefit from it too. To start with, unless the think you are making is very small, its best to build off of an armature. You don’t want more than about a half inch of solid clay in any direction. 
I could write a ton about armatures, but the most important things for this write up are, that it has the shape/size/structure you’re going for, somewhat strong, able to withstand some heat; thin plastic is a mistake. Wire/wood and balled-up aluminum foil are great.
Clay
There are a few different types of polymer clay and each one has its strengths. Fimo comes in a variety of colors and is slightly warier than Sculpy.
Sculpy 2, i.e. the pink stuff is softer and great for sculpting by hand, laying up a bunch of material, covering space and blocking it out. The slight flesh-like translucency can be nice, but can be a bit too soft. I would find myself smashing a part while working on another.
For detailing Sculpy Firm is the best, but it can be a bit too hard, especially for fast/expressive stuff. It’s also a bit more expensive than regular Sculpy and most stores don’t keep it in stock.
One way to cut down on the softness of new Sculpy is to leach some of the oil out of it, you can do this by flattening it out to get more surface area and sandwiching it in paper. The paper draws the oils out, giving you a firmer/waxier clay.
My favorite is a mix of polymer clays depending on what I am doing, Fimo, Sculpy Firm, Sculpy2 and Sculpy moldmaker. Mixing clay is best done with a pasta machine, run it through, fold, repeat.
I like to cut Firm with a dab of sculpy moldmaker, which is super soft/sticky, but hardens with a little flexibility when you cook it, so makes it a bit less brittle in the end. A little goes a long way. I tend to just use Fimo to tint if I don’t want to paint it or just use transparent paint, since its available in a variety of colors.
Tools
As for tools there are a few I like and tend to reach for first;
Loops
Loops/saw rakes – These are good for evening out a broad surface, creating a coarse texture, I use an old hacksaw blade, heated and bent as a rake tool, something like this;
Block
Paddle – I will often grab a piece of scrap wood to have a flat surface to press and roll, to even out bumps and inconsistencies, compressing, and to bring a section of clay down.
Flats
Flats/blades – flat tools have a couple ways to be used; Spreading/smearing with a broad surface, like butter or cream cheese on a bagel. This is good for blending in outwardly rounded convex shapes. Chiseling can be done to create angles surfaces.
Rounds
Ball/spheres – This is a subtle difference, but it changed the way I worked and thought about shape a bit so I wanted to try and explain. Clay sculpted with flat tools tends to have a choppy convex shape, with material extending out from the mass and clay blended with rounded tools tends to be the opposite, mashed in towards the center.
Round ended tools are extremely useful for the concave surface. Like pushing in the inside of a nostril, a socket, or the curve beside the eye to the bridge of the nose. Anywhere that you have a bowl-shape.
Sharps
Blades – knives, needles, dental tools, are good for sharp lines. Poking and cutting tends to leave scratches or gouges, basically a V shaped impression. This is what you would want when making the depression between two rounded masses, like the lines and wrinkles in a forehead, or butt-crack.
Nibs
Rubber nibs – there are a wide variety of these available, its good to have a variety of shapes and hardnesses. These are purely personal preference, and for me they feel a bit like calligraphy pens. The softness of the rubber can tone done the choppy nature of knife/wedge ended tool They are great for smooth arching shapes and blending, but they have a distinct shape, see above round vs flat.
Stamps
Stamps – I can think of two types of stamps I use, I’ll call them; cookie cutter type and texture mats. Most of the cookie cutter tools I use are just bits of brass tubing; useful for stamping a circle, or a compressed circle which makes good stitches. 
Texture mats are easy to make, you can paint latex over whatever has the surface texture you want to copy then peel it up. Its as easy as that. Since this is a surface detail it would be one of your last steps.
You will eventually get to a point with the sculpt where its mostly there, blocked out, and you want to blend parts, or work the surface for texture. Dryish clay has a bit of ‘grit’ to it. You can see this when you drag a tool across or spread it. Its a really fine texture, but can be annoying when you want to make something with clean/smooth texture, or when trying to blend. This blending is much easier with something to soften the clay again, I like translucent liquid sculpy and baby oil. I will keep a puddle of it on a pallet and dip my tools in to get them to glide more evenly. I think of it as welding the surfaces together.
You can even paint baby oil onto the surface of the clay to soften it a bit. Another reason you may need to soften the surface a little is before applying a texture stamp,
Firing
When you are happy with your work and want to save it, its time to cook it, or fire it. Applying heat to harden the clay. Don’t feel like you have to stop working on it after you fire it, its perfectly alright, and encouraged even, to work in stages and fire it multiple times. There are a few ways to do this. People talk about the time and temperature to cook it in the oven, and I see people use dedicated toaster ovens for it too. You can boil it, just make sure there are air-holes to release pressure if it has a hollow armature. But my favorite way to cook it it the heat gun.
Using a heat gun lets me apply heat directly to a section and leave another alone if I want. I hold the heat gun a 5-6 inches away from the work and keep it moving in little circles to evenly distribute the heat.
Keep a close watch of the surface of the clay, you will see as the oils evaporate from it and it takes a slightly darker more matte finish. Thats when to stop!
Before;
After;
Shortly after that shift it will go very dark and bubble, burning. That is not necessarily a bad thing, and sometimes that is a desirable effect too, but it can be heartbreaking to scorch the carefully detailed work.
Thanks for reading!
(not bad for something I made just to show how the tool marks look in clay, I like him!)
