How do you put guide lines in photoshop when working?

I want to make sure everything lines up in photoshop and I know i've seen pple in tutorials have guides that are lines to make sure and I think they are yellow. How do you get them?

Go to View > Rulers or press Ctrl (Cmd) + R. From rulers you can drag guides. If you want to change the guides color place the mouse cursor exactly on a guide and double click. The View menu shows some options about the guides (lock, snap to etc.).