Simplifying the model
One of the problems with Dynamic Topology is that meshes can quickly gain a lot of polygons making a more complex shape. With high polygon models even powerful computers can slow down. Fortunately, it is easy to reduce the number of polygons in a model often without making any visible difference in the model, while reducing how hard the computer has to work.
In the modifier tab on the Properties panel on the right press the Add Modifier button and select the Decimate modifier.
Decimate works by entering a ratio between 0 and 1 and reducing the polygons in the model until they match the ratio. So to reduce the polygons to 1/10 of their original count a ratio of 0.1 would be entered. Decimate attempts to remove polygons that won't be noticed, but if the count is reduced too much it becomes very apparent. The following illustration is the teddy bear model at about 100 polygons, 200 polygons, 500 polygons, 900, and 9000, and 90,000 polygons:
There comes a point of diminishing...
