One of the best drawing surfaces is Cartridge paper, it can be purchased in various sizes and thickness. You will tend to draw on A3 or A4 size paper (This page).
A0 (1189 x 841) is the largest, then A1 (841 x 594), A2 (594 x 420), A3 (420 x 297), A4 (297 x 210) A5 (210 x 148) and A6 (148 x 105) would be ideal for a sketchbook suitable for fitting in a bag or pocket.

The thickness ranges from 95gsm which the pages are very thin, these pads average approx. 50 sheets, they can be supplied up 240 gsm in weight which is, very stiff and card like, however you only get approx. 20 pages in these pads.

You can of course draw on any surface from cheap lining paper to expensive Ingress paper, but Cartridge is ideal all round surface for pencil, pen and ink, charcoal, watercolour, marker pens and many other mediums.

Paper - Bristol Board
The best surface you can work with is Bristol board (Canson Bristol Board A3, A4) this is a stiff, very smooth, layout card. You can also use Cartridge paper, Watercolour paper, Coloured Card, etc. thin paper is to be avoided as buckling of the paper can occur when applying a lot of ink.

Paper Surfaces (Watercolour)

• Rough - Natural surface of paper when dry.
• Not (or cold pressed) - Between Hot Pressed and Rough
  (pressed between cold rollers)
• Hot Pressed - Smooth finish sometimes pressed between hot rollers.