Stoneware is fired hot enough that the clay body vitrifies, which means it stops absorbing water. That single fact decides most of the advice below.
Thermal shock is what actually breaks it
Almost every cracked piece of stoneware was cracked by a fast temperature change rather than by use. Boiling water into a cold mug, a dish moved from the fridge into a hot oven, cold water run onto a hot platter: the outside of the wall changes size before the inside does, and the piece splits. Let pieces change temperature along with whatever they are in. A dish that is going into a hot oven should start in a cold one.
The dishwasher is fine, the loading is not
Vitrified stoneware is dishwasher safe on a standard cycle. Detergent does not etch it the way it etches glass. What does damage it is contact. Two plates leaning against each other vibrate for two hours and chip at the rim. Load with a gap, and keep the unglazed foot ring of one piece away from the glazed face of another, because the foot is the harder of the two.
Crazing, and whether it matters
Crazing is the fine network of lines you sometimes see in a glaze. It happens because the glaze and the clay body under it shrink at slightly different rates as they cool, so the glaze ends up under tension and relieves it by cracking. It is a glaze effect, not a break in the piece.
On earthenware it matters, because the body underneath is porous: liquid gets through the glaze, the piece stains and eventually weeps. On vitrified stoneware the body does not absorb, so crazing is cosmetic. The lines may darken over years as tea and coffee settle into them. That is ageing. If a crazed piece ever holds an odour, or shows a damp patch on the outside after it has been standing full, stop using it for food.
Stacking
Stack plates no more than six high and put something between them: a felt pad, a coffee filter, a folded square of paper towel. The unglazed foot ring is fired clay with no glaze on it, which makes it harder than the glazed face it sits on, and it will leave grey rings on the plate below. Bowls nest safely because they touch rim to wall rather than foot to face. Mugs should not be stacked at all, because handles are the first thing to go.
Marks from cutlery
Grey lines on a plate are metal deposited on the glaze by a knife or a fork. They are not scratches in the surface, and they come off with a paste of bicarbonate of soda on a damp cloth, or with a cream cleaner used sparingly. Do not use a scouring pad, which will dull a satin glaze permanently and cannot be undone.
Microwaves, ovens and flame
Everything in the range is microwave safe unless the product page says otherwise. Oven use is listed per product with a temperature, because it depends on how thick the walls of that particular shape are. Nothing here is safe under a grill, on a hob or over a direct flame.
Glass and linen
Free-blown glass is dishwasher safe but stays clearer if you wash it by hand, because detergent etches glass over hundreds of cycles and the cloudy film is permanent. Linen goes in the machine at 40 °C and irons best while damp.
Food contact
[Client to confirm food-contact and lead or cadmium testing for the glazes used, the standard tested against and the date of testing, before any food-safety statement is published on this site.]