The paper you choose to use will affect the outcome of your work, so chose the right paper for you.

The weight and surface texture are also important, as well as your choice of using loose sheets or working in a pad or block. 

Ideally if you are painting watercolour in a traditional wet way, then 140lb 300gms thickness for sheets up to 1/4 Imperial in size (11 x 15 inches) is perfect. There is no need to stretch your paper.

A rough surface paper is fabulous for creating textural effects in landscapes and botanical/foliage paintings.
A not surface paper is well suited for painting figures, reflection in water, and more detailed flower/foliage works and stroke work.