You are exactly right when it comes to establishing proper fundamentals early on. If you sometimes wait too long, you may have already created bad habits that are tough to break.
My recommendation is to try and take an in-person lesson with a local shooting instructor that has a track record of knowing what they’re doing or at least certified. This can be a great start to getting proper fundamentals you can build on.
When it comes to more of a deep dive, there are multiple types of online videos, CD’s, and tapes from proven champions available for purchase. There are also some fantastic books. All shooting styles and methods are different you just have to find out what works best for you. Anthony Matarese Jr., Zachary Kienbaum, Gebben and Karen Miles, and many more offer instructional videos and or books for purchase.