I often get asked over at www.DrawMe.com.au how I draw a caricature.
First, you need a little artistic ability and a lot of patience.
Next, you need to be creative in your output. Think about what you are designing and try to follow basic design principles.
If you are just starting to draw caricatures then visit other caricature websites and review the work of the artists. Each has a unique style.
You need to decide what tools you will be using to draw your caricatures. The cheapest option is just to use a basic pencil. You may find that a softer pencil is easier to work with and is more forgiving.
Charcoal is another option but can be somewhat messy for a beginner.
Many artists have now made the switch to digital mediums and use a digital graphics tablet such as the popular Wacom brand.
If you are going digital then consider the expense of tablet, computer, and software.
Many artists use Photoshop as their main software although some do use Illustrator or other vector based programs.
If you have used a pencil for your drawing then making the switch to digital pen/tablet should not be too difficult.
The first few weeks can be tricky when using a digital pen, especially if you have been used to using a mouse. Stick with it. It does get easier. I used a mouse for many years and found it quite tricky to make the move to digital pen. I now find it quite annoying to have to use a mouse. I love using my pen to draw my artwork.