What's the best way to create custom grid lines in Photoshop?
Is there a way to quickly define a baseline grid on photoshop using the guides tool? For example, if I want to create a 24px vertical rhythm, can I do this quickly on PS?
Use the Grid, Luke...
Preferences > Guides, Grid and Slices and set up the grid you want. Show/hide the grid with Ctl-', and ensure
View > Snap To > Grid is checked.
Unlike Illustrator and InDesign, you can't make a distinct baseline grid. The above should be enough for most purposes, though.