If you're creating a logo, then you should make the document 300 dpi. I usually create logos at 3000px by 3000px at 300 dpi.
Once you are happy with the logo, save it. Then save a copy of it and scale the copy down in size. This will allow your logo to retain a crispness and sharpness. No pixelation.
Even better, use Adobe Illustrator. If you don't have illustrator then use Inkscape (It's Free).