You can place pixels with the "pencil tool" with 1 size.
This guide will help you a lot if you take some time to read.
i curious with how to made diagonal line with perfect.. Do you know?
First off, nice pieces. Welcome to PJ :)
Photoshop is a fine program for pixel art, but at first, try not to use any tools other than Pencil and Paint-Bucket with Anti-Alias off.
If you use other tools, photoshop may put a lot of colors that you don't want.
That's why we say: "You need pixel level control in pixel art".
Make more pixels!
@gecimen: I use photoshop.. :) Please critize my pixel. I wanna learn pixel more and more :)
You really don't need 200 colors for this. That was also a problem with your earlier pieces. What program are you using?