Mine arsenic directly
One of the best ways to obtain arsenic is to mine the element directly. Deposits of pure arsenic, which occur naturally, are too small to be commercially mined but you can do that individually.
Heat orpiment with soap
The method of obtaining arsenic through heat orpiment (As2S3) with soap was revealed vaguely by Albertus Magnus in the 13th century.
Reduce White Arsenic
White arsenic (As2O3), which is also called arsenolite, can be reduced with charcoal. By heating, you will get the following reaction: 2As2O3 + 3C + heat -> 4As + 3CO2. This method of obtaining arsenic was properly elaborated by Johann Schroder in 1649. By heating arsenious oxide (As4O6) with carbon, arsenic is prepared in laboratories these days with a similar reaction.
Dig arsenic mines commercially
Many commercially important minerals like realgar, arsenopyrite, orpiment and loellingite contain arsenic. It is most commonly found in arsenopyrite. In the absence of air, these minerals are heated at 700 degrees Celsius and as a result, arsenic sublimates come out of the minerals in shape of a gas.
Obtain arsenic as a by-product
You can also obtain arsenic by refining other metals and as a by-product of mining. The flue dusts produced from copper, nickel and tin need to be recovered. They are extremely high in arsenides of these metals. Arsenic can be sublimated by heating them in air. You can now condense the gas back into solid form by cooling it. Most of arsenic in the world is produced by this method.