In case the rendering geometry needs to be much more detailed than the simulation geometry, you can often address this issue by adding a Subdivide SOP after the DOP Import node (that reads the simulated cloth geometry). In case you're using Mantra to render the final results, you can omit adding the Subdivide SOP and select the Render As Subdivide option on the object that holds the cloth geometry.

There are other situations where you must animate a given model and you can not simply subdivide the simulation geometry. Often, the geometry that’s used for rendering the cloth is not very suitable for simulation purposes. The number of polygons in the rendering geometry may be too high, and the shape of the polygons on the mesh may be ill-suited for nice looking simulations. In that case, it is possible to use a different geometry for simulation and transfer over the motion from the simulation geometry to the rendering geometry. This can be done using the Cloth Capture and Cloth Deform SOPs.