First, if you have any good video tutorials, I'd love to check them out. If you're up for diagnosing my needs, read on... January 7, 2017 UPDATE What I've found is there are a lot of conflicting ideas about left hand bass technique. Why this is is because of ergonomics. Everyone is unique and different. There are, however, some general guidelines people should look into related to left hand technique to develop the technique that suits your needs ergonomically and musically. The truth about left-hand technique is that it is not reasonable, or wise, to presume you must maintain a strict, rigid form. Or even to presume there is a one-size-fits-all standard technique for everyone. In fact, attempting to force a strict form may well open you up to pain and eventual injury. I know I was experiencing pain very quickly upon applying some of the strict guideliness noted in some of the tutorials noted in this very thread. Really, your left hand should adjust depending on position to avoid excessive wrist bend or unnatural finger/thumb forms (again, this is different for everyone and depends upon ergonomics) as you go up and down the neck. That includes allowing for rolling your thumb over the top of the fretboard if you're fingering above the 12th fret. To do otherwise would place almost anyone, regardless of ergonomics, in a position that is quite awkward unless they have their bass under their chin. So... because of ergonomics there is no standard rule of "thumb," pardon the pun, outside of the general rule of giving enough support for fluid fretting which sounds the note well. And that support should not require a high level of resistance. Depending on the size of one's hand, the thumb should be placed foremost in a comfortable position, and secondarily a position that affords whatever support is necessary in that allows for fingering that is efficient and makes for clear, clean sounding of a particular note. In other words, kind of like Fergie proved, the thumb position is not as important as people think, and should be adjusted to suit the particular player ergonomically and musically (ergonomics being foremost to avoid injury). In short, the only bad left hand technique is a technique that leads to injury, causes poor tone, and leads to inefficiency of movement. In consideration of this, I have decided to develop a technique that suits me ergonomically that best helps me to avoid those three issues. And my advice to everyone else is to do the same unless you find a particular tutorial suits you ergonomically and musically, which is entirely possible. I do not presume to charge anyone pushing a particular form in any of the videos or tutorials in this thread to be in error for their own ergonomics, but that they are in error presuming everyone needs to do exactly as they are doing to meet their own personal needs.