The best idea is to buy through a reputable nursery or carnivorous plant society. There are many enthusiasts out there who produce fantastic quality specimens.
You may purchase many cultivars through this site. We source all of our specimens from only the best suppliers to ensure quality.
A lot of other good sellers can be found on the UK Carnivorous Plant Forum
Be very wary of plants from garden centres and local nurseries. These plants are often marketed and treated like novelty items. They are given nowhere enough light and are often fed using standard tap water and fertilizer which are not recommended.