This will depend on the type of media you are using (pencil, watercolour, acrylics etc.). Paper is important because if the surface is designed for your media then the results will be better.  The range of papers available is vast and it can be a bit bewildering in the art stores to know what paper is for what.  There are several factors to consider; paper weight, paper texture, paper colour and paper size.

Paper Weight

This means how thick the paper is and is measured in gsm (grams per square metre).  Most drawing paper (called cartridge paper) is 100 – 200gsm which is fine for drawing with pencil, charcoal, pastel pencils, conte crayon and drawing pencils.  Painting requires thicker paper – at least 300gsm or a more specialised type of paper that can deal with the medium.

Paper Texture

There are choices of grainy or smooth in most types of paper.  Cartridge paper for drawing is mainly smooth but you can get a grainy paper which is suitable for charcoal.  Pastels require a grainy paper or paper with a ‘tooth’ to grip the pigment.  I would recommend pastel paper because it comes in different colours other than white which give better results and the surface has a good ‘tooth’ designed to hold pigment.

Watercolour and acrylic papers also have choices of grainy, rough or smooth.  Smoother papers are better for fine details.  Rough papers are good for creating texture.

Below is a list of the types of paper you will need depending on the medium you are using:

Pencil

Cartridge paper mainly but you could use grained drawing paper, pastel paper

Pastel

Pastel paper

Charcoal

Grainy cartridge paper or pastel paper

Watercolour

Watercolour paper – smooth (hot-pressed) for detail and rough for texture or looser work

Acrylic

Canvas, board, wood (primed) or acrylic paper – could use watercolour paper primed

Oils

Canvas, board or acrylic paper – could use watercolour paper primed

If you are thinking about buying a sketchpad and don’t want to get all the different sorts for each medium what should you buy?  A good quality cartridge paper should be able to cope with small experiments in paint media and a Mixed Media sketchpad is a good choice for an all-rounder too.  See my post Which Size Sketchpad? for more advice.