Realize that you probably want topsoil, not just 'dirt'. Ask for cheap 'dirt' and you may get 'fill'. 'Fill' is comprised of broken concrete, clay, gravel, tree stumps, and anyting else people can find that takes up room, like their mother-in-laws.
Topsoil itself comes in many flavours, and yes, people who know may test the soil by tasting it. Bad topsoil will have a large amount of inorganics (sand and clay) that do not promote plant growth, and may contain a lot of weeds.
'Triple-mix' is a common phrase used, albeit incorrectly by some. It should be your best bet.
Ask at local nuseries, who provides the best topsoil in the area.