I am total newbie and I always fails to fly A-10 stable using keyboard.the pitch rise to 30 or 40 degree then down to 30 or 40 degree and repeat. i just slight touched the arrow key.

Any have some tips?

its sounds predictable, but you should buy a fligt-stick, there are many low-budget of these boys:P
Its nearly impossible to paly the game without a stick.
ps: the Saitex X-52 is known to be very good, bet expensive, Try to get a HOTAS system
Good luck and good hunting

Err..
Thank you.

Onion- you're asking a wide open question that few are going to bother responding to. The answers are on a scale sufficient to fill 2 novels.

Get a flight stick, & start reading.

Start with these forums- use the search. Then look at some of the fan sites for different takes on the many aspects of flight simulation.

Click my sig to read mine- geared towards nuggets. Hardware recommendations, setup, downloads to make learning easier.