Carding is another step towards consistency in your yarn
Like everything there are many ways to do something and I have felt there are no wrong ways, only the way that works for you. But to find this you need to learn at least the basic principles such as; how much fibre should you load onto your cards? Or should you start carding from the top of the card, or from the tip, is changing hands a heresy?. These way will give a different effects to the finished yarn and therefore the finished product. For each of these questions there is no finite answer.
For carding there are hand-cards, which are two paddles that have wire bards covering one side of each, these would be the most accessible tool available and the hand-carders produce those fluffy, lofty, spinnable rolags. Then there are Drum-Carders of various sizes.
These are available when you want to achieve greater quantity and a different presentation of the fibre. The drum-carders producing those wonderful fanciful batts.