Positive charges generate an electric field that can be represented by arrows leaving the charge. Positive charges placed in this electric field experience a force in the direction of the arrows, and hence when two positive charges are placed near each other, each experiences a force away from the other (in the direction of other charge's 'lines of force'). Similarly, negative charges generate an electric field that can be represented with arrows pointing towards the charge, and negative charges placed in the field experience a force in the opposite direction to the arrows. Again, when two negative charges are placed near each other, they each experience a force away from each other (in the opposite direction to the other charge's 'lines of force'). Hence, like forces repel, and to diagramatically represent this, draw two like charges and their lines of force, and note the direction of the forces experienced by both charges.
When a positive charge is placed near a negative charge, it experiences a force towards the negative charge (in the direction of the negative charge's lines of force). Similarly, the negative charge experiences a force towards the positive charge (in the opposite direction to the lines of force of the positive charge). Hence, unlike forces attract. Same thing for the diagram here.
I hope that made sense - it's harder to explain 'on paper' than verbally.
I_F