Rules for drawing lines of electric force

[physicsexpert]

1. The number of lines leaving a positive charge or entering a negative charge is proportional to the charge.
   
2. The lines are drawn symmetrically leaving or entering a point charge
   
3. Lines begin or end only on charges.
   
4. The density of lines (number per unit area perpendicular to the lines) is proportional to the magnitude of the field.
   
5. No two field lines can cross.

Note:- This rule number 5 follows from the fact that E has unique direction at any point in space.