Invoking spirits

Acording to my knolage you can summon/invoke good spirits such as your spiritual guides, astral guides, dietys, and higher spirits to invoke for ritual purposes as for other minor spirits or ghost you shuld use an evocation but I suggest you don't try an evocation if you don't have expiriance with spirits in general.

I agree with Athena, It is not recommended, especially if you don't have a good reason to do so. Don't get ahead of yourself, magic has no shortcuts.