Simply look up the characteristics of the cactus in the field guide (types of flower, size, shape, color, etc) and see if you can find a cactus that closely resembles yours. While you may not find an exact match, at least the closest entry will point you in the right direction.
Also question is, what is the most common type of Cactus?
The round type cactus: the most common is the Echinocactus grusonii.
Furthermore, are cacti Tropical?
In tropical regions, other cacti grow as forest climbers and epiphytes (plants that grow on trees). Their stems are typically flattened, almost leaf-like in appearance, with fewer or even no spines, such as the well-known Christmas cactus or Thanksgiving cactus (in the genus Schlumbergera).
How many types of cactus are there?
How long does a cactus live?
In the wild cacti can live for hundreds of years. Indoors they may survive for 10 years or more.