French Curves:

These tools come in several different sizes and shapes. I use at least 4 on any given drawing. You rotate them around on your drawing till you find an egde that closely matches the curve you're trying to ink. You can also purchase a "Flexible Curve" which looks like a peice of rubber railroad track. It's no good for tight curves but works nice on long curves.

Triangles:

A must have for Comic book paneling and perspective work. The triangle rest on your T-Square. Use the T-square to draw Horizontal lines and the Triangle to draw Vertical lines. The 45 degee angles com in andy for drawing perspective lines back to the "Vanishing point". I'll cover perspective in another tutorial.

Ruler with Inking Edge:

Really, all your tools should have an inking edge. Notice the diagram on the left depicting the way an inking edge works with a Pen. The Ruler edge is raised from the drawing surface allowing the ink to apply cleanly. If that edge was flat on the paper the ink would bleed between the edge on the paper making an ugly mess.