When you are standing up, you'd better to see the place of your Sajdah.
(Shia Muslim, look at the thing on which they Sajdah, such as Turbah)

When you are in Qunut, you'd better to see the palm.

When you are in Roku', it is better to look at the place which it between your two feet.

When you are in Sajdah, it is better to see toward your nose.

When you are in Tashahod, it is better that you see to your skirt ( or toward the tip of knees)

(Imam Baqer (a.s.) taught it to someone (for Roku', Sajdah, Tashahod))

**Sources**:

http://www.askdin.com/thread36833.html

http://www.jamnews.ir/detail/News/185002