Create a new layer. Decide on the vanishing point(s). Use the Line tool (set to Fill Pixels) to draw lines radiating out from the vanishing point(s). Simple enough. Then you can turn this layer on and off as necessary, and use Hue and Saturation to adjust the color, if wanted.
That's a good method if you need regularly-spaced lines and/or you want to go for some more complex perspective. But there's a lot to be said for the quick, easy feel of just drawing in the lines yourself.
yeah i usually just slap a grid in quickly with my tablet since a roung grid should serve you fine...then just work on another layer, unless you want that grid to show....then it would probably take a bit more work.