You shouldn't waste any time. The first few seconds is where everything happens. If you start with "hello guys welcome back..." I have noticed that a lot of people would scroll to another video before you even reach the point you want to make. Just go straight to the point very quickly. I notice that videos that grab attention immediately pulls me in more, especially when I'm just scrolling my phone to while away time or when I'm looking for anything that could kill boredom. We need to understand that people's attention these days are so short.