According to R Dhillon good precis should contain following points
1) understand the given passage well.
2) Mark or underline the points or ideas.
3) Prepare the rough draft in your own words, avoiding every superfluity.
4) Give only the views of the author of the passage.
5) Use only indirect speech, third person and past tense.
6) Be Careful of the opening sentence of your precis it is important.
7) Mark the central idea in each paragraph.
8) Your precis should be simple, concise, clear, a coherent narrative.
9) Revise your draft keeping in view the above points.
10) Do not forget to give a suitable title to your precis.