Hi Ming Wu,
Today people can invest and trade in most of the markets around the world.
The markets offer a lot of opportunities and you can take advantage of this continually.
The better strategies for optimizing returns over time are many and they vary greatly.
Using a logical approach is called for. That is all that matters. There are no tricks or special things required.
Edit: Returns overlap greatly from market to market.
A passive account (you let your broker trade it for you) would give you about 60% a year.
If you do the work yourself it is much greater.