There's no one answer to this question; each clay brand has its own strengths and weaknesses, and different clay artists have different preferences. Some of the available brands are:

Sculpey Polyform Products Co.

There are three types of Sculpey:

• The original Sculpey comes only in white, in 2-lb boxes. It is a soft clay, very brittle and chalky when fired, and is the least expensive of the clays.
• Super Sculpey comes only in flesh-tone in 1-lb boxes. It's stronger and more flexible when fired than original Sculpey, sometimes used for doll-making.
• Sculpey III is most often used by clay artists. It comes in about 40 colors in 2-oz packages, and is usually easy to find. Sculpey III is the softest and easiest to condition of the commonly available clays; however, it gets softer the more it's worked, and easily smears when used in canes. (You can work around this problem by chilling your Sculpey canes before slicing them.) Sculpey III develops a slightly porous, matte finish after firing, which looks especially good with dark colors, but does not buff to as high a shine as finer-grained clays and is not as strong when fired.

The colors are strong and may overwhelm colors in other clays when mixed; if you're mixing Sculpey III with another clay brand, start with small amounts of the Sculpey III and watch the color. The light colors seem to be mixed with white and can be a little dull. This clay comes in about 30 colors, including translucent, brights, metallics, and fluorescents.

Premo Sculpey Polyform Products Co.

This replacement for Promat is the newest of the clays. This brand is fairly soft and easy to condition, but holds detail in canes well. The colors are drawn from a "painter's palette" of warm and cool blues, yellows, and reds, so those with a background in color theory will find it easier to mix custom colors to their own specifications. Premo was developed by the Clay Factory, and earlier versions were known as Clay Factory Clay (CFC).

Fimo Eberhard Faber

Fimo is a widely-available polymer clay and probably the most popular among clay artists, although you may not be able to find all of the colors locally. Fimo comes in 58g (about 2 ounces) and 350g (about 12.5 ounces) packages. It is the stiffest of the clays and the most difficult to condition. Fimo's firmness lets it hold very fine detail in canework; smearing is rare. When fired, Fimo has a slightly glossy, "plasticky"-looking surface. It buffs well and develops a high shine. Fired Fimo is very strong. Fimo has a very beautiful selection of colors, including two transparent clays, six "stone" textured clays, a glow-in-the-dark, and metallics ("perlglantz"). There is also a soft formulation of Fimo that comes in a different selection of colors.

Promat Polyform Products Co.

Promat is made by the same company as Sculpey. Promat differs from Sculpey in being firmer in texture - harder to condition, but less prone to smearing, stronger when fired, and flexible in thin sheets. Promat has a relatively limited selection of colors, including excellent pearlescent colors. This brand is being phased out by Polyform as Premo is introduced.

Cernit T&F GmbH

Cernit is the strongest of the clays. It has a porcelain, waxy finish when fired and is often used for dollmaking because of this quality of the fired clay.

Friendly Clay Amaco

Available in packages and as pre-made canes, ready for slicing. Amaco also sells glazes, metallic powders, and molds for use with polymer clay.

The best brand for you will depend on what you want to use it for, and also on your personal preferences and how you like to work with with the clay. The Polymer Clay Central FAQ includes a comparison of clay brands; so does the Grin and Bear It Clay Art page. Some of the clays are available in sample packs that let you try several colors in small amounts. You can also mix different brands of clay to get the level of softness, color, and other qualities you want.

For making beads or covering objects, any of the polymer clay brands will do fine. However, if you're making objects (such as boxes, picture frames, etc) from clay, or creating buttons or thin pieces that must hold up to handling, you'll want to select a strong clay such as Fimo, Promat, or Cernit. If you want to use a weaker clay such as Sculpey for such pieces, first make the base piece from a strong clay, then apply the weaker clay as a veneer over it.

There's no problem with mixing different brands together, and you may want to do this often to obtain the properties of both clays. For example, many clayworkers mix Sculpey with Fimo to get a clay that's easier to work than Fimo, but stronger than Sculpey. You mix clay simply by conditioning the two kinds together, or by working conditioned clay until it's thoroughly blended.

This depends on your personal preferences, but there are a few guidelines that will help when you're making canes. Finely detailed canework depends on contrast between the parts of the design, so place light clays next to dark ones. Often, the impact of a piece is increased when you use related colors - for example, a warm orange-yellow with a warm dark brown, or a series of shades of cool blue. Metallic clays used with black create a striking effect. Try different combinations - the same design can look completely different when made with a different set of colors.

If you want to use two clays of about the same lightness in a cane - for example, a pink with a yellow - try wrapping one or both with a thin sheet of a contrasting dark color, such as black or navy blue. When the cane is reduced, this sheet will become a very thin layer that will help set off the pink from the yellow parts of your design.

(Fimo burgundy has been known to sometimes bleed into lighter colors after firing, so avoid placing this color next to a light one.)

You may be perfectly happy with clay right out of the package; Fimo in particular comes in some beautiful colors. However, sometimes you can't find just the right color in the clay brand you want to use. Here are some tips for mixing colors:

• To make intermediate (secondary) colors, add together two primaries that tend toward the color you want. For example, to make orange, combine a warm red (one with no tinge of purple) and a warm yellow (one that's a little orange, rather than a little greenish). Adding a cool (greenish) yellow to a greenish blue will make a bright green; but adding a warm yellow to a cool (slightly purple) blue will make a dull green. Adding red and blue will make purple: a deep bright purple if you choose a slightly purplish red and blue, a dull brownish-purple if you choose an orangey red and a greenish blue.
• To make a color less bright without changing its value, add transclucent. You can also add white, but adding too much white will lighten the color as well as making it less bright, an effect you may not want. Add up to a third of translucent clay for this effect.
• To make a semi-transparent wash of color, add colored clay to translucent. Start with a pea-sized ball of colored clay to a golfball-sized ball of translucent clay.
• To brighten a color and give it more "punch", add a small amount of fluorescent clay in a similar color. For example, to make pink brighter, try adding a little bit of fluorescent orange.

Remember to start with the main color and mix in small amounts, gradually, to avoid going too far - for example, to make a translucent red, start with a lot of translucent and mix in small amounts of your red until you get the effect you want.

When two colors of clay are thoroughly mixed, the distinction between them disappears. However, if you stop the mixing partway, you'll get a streaked effect similar to marble. (Make sure not to stop mixing in time to preserve the marbled grain you want; continued handling of the clay will mix it further.)

Different color combinations can give you the effect of various semi-precious stones: for example, marbling several shades of green with white produces a clay that looks like malachite. Marbling earth tones and translucent gives the effect of agate. Pearl white with small amounts of dark gray and translucent makes a good marble.

You can vary the marble effect by mixing the clay in different ways. Roll the partially-mixed clay out into a thin snake, or pull it, to obtain narrow streaks. Running it through a pasta machine one or more times produces a different sort of streaking. Repeatedly twisting and folding the partially-mixed clay strands can make an effect like natural amber. Once you learn how to marble the clay, try different techniques at different points in the mixing for subtly different effects.

You can roll out the marbled clay and use it to make (or cover) flat items such as boxes and frames, or roll small bits of the clay to use as beads. Large marbled beads are especially effective. You can also use marbled clay as part of a cane design.

Many clay artists use continuous shades of a single color, from light to dark; the work of City Zen Cane in particular makes much use of this technique. One method of obtaining such a gradient is simply to mix seven or eight shades by combining the base color with different amounts of white, then flatten each shade into a sheet and stack the sheets in order from dark to light.

An easier method for mixing a gradient has been described by Judith Skinner: you make a triangle of white and a triangle of the color you want to blend, put the long sides together to make a rectangle, and run this sheet repeatedly through the pasta machine, folding it in half each time, until the colors are blended together. You can use this same technique to blend two colors, or even use several tall triangles (instead of just two) to create a multi-color blend.