Be prepared that planting and owning a dahlia does takes a fair amount of work and attention because this hungry flower will not let neglect go unpunished. Exactly how much work the dahlia needs depends, though, on how much work has been put into the soil before the dahlia was planted and where (geographically) in the world it was planted. In some colder climates, one of the easiest strategies is to plant the dahlia in a pot and just take it inside when the weather is nasty and bring it out to enjoy the outdoors when the temperature will not drop below freezing.
Although the dahlia is one of the most versatile, beautiful and special flowers in the world, it is also the "cookie monster" of the garden. The dahlia is a hungry beast that continuously needs to be fed in order to please its master with its gorgeous flowers. If the soil had lots of manure or compost worked into it before the dahlia was planted, it will save you a lot of time; otherwise there is a lot of feeding to consider in order to help the dahlia reach full flowering ability. The fact is, liquid fertilizer is not sufficient nutrition for a healthy dahlia - it needs real food blended directly into the soil. Also remember that the dahlia needs a lot of sun and a constant supply of water in order to make use of all that nutrition (of course remembering not to overwater and make the bulb swim in water!)
This might not be of concern for those living in tropical climates but the fact is a single frosty night might kill the dahlia all the way down to the bulb. In these conditions you need to consider overwintering the dahlia. In climates where the temperature might drop below zero and dahlias are still planted in the natural garden it is possible to save them through winterization. This means that once the temperature starts to drop, the dahlia is cut down and the bulb is dug up from the ground. The dahlia bulb is then carefully washed in water and dried with either an ordinary towel or a paper towel. The main idea is to wash away all the dirt that might carry diseases. The dahlia bulb is then placed in a dark, dry and very cool spot, a few degrees above freezing is optimal. The bulb will with most certainty lie dormant over the cold winter and will be ready to be replanted in the spring.
Although not very hardy when it comes to cold, the dahlia can take a lot of abuse from the gardener’s knife. The dahlia is very easy to prune and shape into any creation one likes and the main idea is that the more flowers one cuts away, the bigger the rest will become. It is actually possible to create one super-sized dahlia flower simply by cutting all of the others away in the early stages of development. Why not do this with a potted dahlia and place it on the kitchen table when guests are coming over? It is a guaranteed conversation starter.