This can be accomplished by making a potting soil using as a component materials such as; perlite, pea sized pumice, or even pea gravel. The trick here is to produce a soil that has some organic mater, but not so much that it becomes water logged and rots your plants roots.
Do not use sand as it is too fine and clogs the pores in the soil. If using a peat-based potting soil, remember that peat decomposes in a few years, resulting in an unhealthy soil. As some Haworthias are slow-growing and can stay in the same pot for years, there may be a tendency to forget to repot into fresh soil, a practice which should be done every 2-3 years.
Watering: It's simple instruction: "water Harworthia when its soil is dry" I got a tip from the Thai cactus collector to test whether the soil is dry or wet: dig the tooth stick into the soil and see if the soil is damp. You can apply another thing instead of tooth stick.
If the plant looks unhealthy, unpot it and inspect the roots. Remove any weak or decayed roots, even back to the stem of the plant. Allow the plant to lie out unpotted for a week, then repot into fresh soil and begin watering carefully until it is apparent that the roots have reestablished and the plant has regained its health.
Light: To put a plant in direct sunlight that has never seen the sun will cause a fatal sunburn. If you place your Haworthias in the brightest light you have that is not direct sunlight, you will grow into very nice looking plants. For growing, a greenhouse is ideal, next choose a sunny South facing window, then an East or West facing window.
Haworthia makes good accent plants on porch, patio, or deck and can be grown outdoors during frost-free periods. Be careful when you move plants outdoors. If they have spent the winter without much direct sunlight, don’t immediately put them into full sun outdoors or they may sunburn. Gradually move them into more direct light over a period of a few weeks.
Harworthia is the slow-growing plant so it doesn't need much fertilizer. If you repot Harworthia often (every year), you don't have to fertilizer. Anyway, when I fertilize my orchid, I give some to my harworthia in the few amount.
If you want to know more about Harworthia such as popular propagation from leaves & roots, containers and pest & disease. I'd like to suggest you to visit the useful websites: www.harworthia.org and http://www.hort.wisc.edu.