What worked for me at first was to take six steps ( paces ), mark the spot then throw several times. If that doesnt work move 6 inchs +/- forward try again if no good move 6" back from origional spot. Find a spot that works and mark it. You will sooner or later find the sweet spot. And you dont have to throw real hard !
Hopefully this will help you , it sure did for me and I throw the VTAC. Also a softwood target is the best ,endgrain if at all possible.