There are probably a ton of tips, but I'd suggest this Top 3:

1. Make yourself familiar with the basics of Bezier drawings: The Bézier Game;
2. Get acquainted with the most important Pathfinder operations Unite, Subtract, Intersect, Divide;
3. Learn the most common complex objects: Group, Compound, and Mask.

Oorspronkelijk geplaatst op Quora: What are the best tips with designing in Adobe Illustrator?"