Consulting a Chinese character by radical and stroke way is a very useful way to look for a character when you do not know its pronunciation.
Take character 吨 as example.
1. Examine the character. What component parts is it composed of? 吨 is composed of two components, 口 and 屯. Identify which components are radicals, and select the most likely one as the radical for this character. In character 吨, the component 口 is the radical.
2. Count the number of strokes in component you have selected as the most likely radical. The number of the radical 口 is three. Search the radical index for the radical beginning with entries containing the counted number of strokes. Turn to the page shown right to the radical 口.
3. Count the number of strokes in the remaining portion of the character. In character 吨, the stroke number of 屯 is four.
4. On the page listing characters under that radical, search the character from the beginning of counted stroke number. See, find 吨 from the beginning of four on the page.
It may take you a little time when you are not familiar with radicals. It really does good as during the process of consulting the character, you have learned the components of it.