R.L. in Adelaide, Australia said: I'm sorry, but I have to put more than just 3.
1) The ability to acknowedge and understand other artworks and artists.
2) Being able to create artwork that can portray different meanings.
3) Knowing the general artistic techniques
4) Patience - not everything works out the way you want it to.
5) Take criticism - you are not creating artwork just for yourself.
6) Able to work under pressure - as you need to meet deadlines.
7) Work with different mediums.
8) creating a style that everyone will know you for (not necessarily if you want more of a range).
I can't think of more right now, but these (I guess) are essential to become the illustrator that everyone wants to hire.
Thank You! I want to become an illustrator, but didnt know what skills i had to have in order to get into the career. This was very helpful! :)