What is the best resolution for 19 inch LCD monitor in windows XP

I bought new LCD Viewsonic 19" inch monitor. I am unable to get good resolution on it. Please suggest me best resolution for the monitor.

I use 1280x768 resolution on my monitor, works pretty fine.

LCD monitors have a "native resolution". They look best at that resolution or multiples of it.
So a monitor with a native resolution of 1280x1024 will look best at:
1280x1024
or
640x512
You can try other resolutions but try ones like 2/3 or 3/4 the native resolution.