It kinda depends on what species you want to keep. Some species have specific requirements.
You can keep them in glass tanks, but acrylic is best for larger clubbers such as O. scyllaris (peacock mantis).
Generally speaking, they're single specimen critters, as they have the ability to kill and eat most fish and inverts. Most will require LR and plenty of rubble, shells, etc to build their lairs (very interesting to watch!). Low light is best, as bright light can bring on dreaded "shell rot".
Stomatopods are also very susceptible to toxins used near their tanks, so never use cleaning products, paint, etc near their setups.