Every caricature artist has their own style and there are many videos and books available on how to draw caricatures.
I suppose, for me, the best advice is to learn your craft and learn how to use your equipment properly.
I draw my caricatures electronically these days i.e. I use a graphics tablet and computer. Some people say this is 'cheating' but if you can't draw with a pencil then you won't be able to draw with a graphics tablet either. In the same way I used a pencil and paintbrush I now use a digital pencil/paintbrush for my paintings. The only difference is it's a lot cleaner!
Using the graphics tablet proved difficult at first but with constant exercises and challenges it became much easier over time.
Drawing caricatures with a graphics tablet is now a pleasure and I often think that if some of the great artists of past years were alive today they would certainly have a go with a graphics tablet.
I start drawing my caricatures with a basic rough outline and then refine this. A base colour and shading is then completed followed by refinements in shadow and highlights.
You will find some of my portrait work on YouTube. The caricatures are produced in much the same way.