Don't la masta here and there.
Me just having some time to share some opinions only.
There are tons of reading materials on the net but I think one of the criteria is when you add up, you add up in small quantities, so that after adding up, your average cost doesn't jump up.
Ya, you can't double up when you average up.

If I am not wrong here... 

Cyclical stock like steel, they have very short profitability one.
So the best time to buy, you buy when they are losing money, or have hardly any earnings.
When there is hardly any earnings, the PE will be high.

When the earnings turn around, the earnings for steel stocks comes in big lump sump.
So the PE will suddenly turn from high PE to low PE.
Anc because the good times for steel stocks tends to be short lived, you then should probably sell when the PE is low.

You probably can use CSCSteel as a reference.

You ask me meh?

I should be the one asking you already.     

U dun be bad boy macam me la.. Dun goreng shares la bro..

Actually.. sharks always do charity work one in the stock market..

You need to make arrangement with investment banks, aka borrow shares from investment before can short sell.

It is called regulated short selling, only certain stock can be shorted that are listed in RSS.

You cannot simply short sell without any arranged borrowed shares from investment banks.

You pendek kasi what saham la?