How to determine when is time to sell your shares?

Everyone must develop your own system to decide when to take profit and leave market for a while.

Here is some of my new theory that i will practice to help me when to sell in future.

Rules
1. When market has PE more than 20.
2. When market has dividend yield less than 2%
3. When index trend is far away from the 200 MA.
4. take Hang Seng index for above rules.

I will try to add in more rules as to help the exit timing in the best time..

Now Hang Seng index:
1. September PE 21.18, for October it is sure more than 21.18
2. Dividend yield for September is 2.04%, for October it is sure less than 2% but the stats have not come out.
3. Trend is far away from 200MA. ( due to surge of almost 50% durng this 2 months)

The latest Hang Seng index shows that it is 36% higher than the 200 MA, which is quite danger.

Seems like i should sell some shares even at lower profit/ loss ? Let me do more research..and think..

If i decide to sell all on Monday ( sure on minimal lose) , it might prove to be a mistakes, but at least you learn and improve.