Hit Control + N to create a new document. Enter 600 in the width and height boxes then click the Advanced button. Select RG, Screen (72ppi) and make sure that the Align New Objects to Pixel Grid box is unchecked before you click OK.
Enable the Grid (View > Show Grid) and the Snap to Grid (View > Snap to Grid). You'll need a grid every 5px, so simply go to Edit > Preferences > Guides > Grid, enter 5 in the Gridline every box and 1 in the Subdivisions box. You should also open the Info panel (Window > Info) for a live preview with the size and position of your shapes. Do not forget to set the unit of measurement to pixels from Edit > Preferences > Units > General. All these options will significantly increase your work speed.