I need some new lines to use to ask permission to detect on someones property..my approach only worked one out of ten times?
Right there is your problem, opening statement "I need new lines" NO single approach, and certainly no pre-rehearsed "speach" is going to work all the time, everyone if different. If you need "someone elses' lines" then you are not a "people person" and therein lies your problem.
I've seen a lot of good ideas in this thread, and some not so good. In no particular order, I've seen Bills approach, a stranger showing up with tooo much info about about the owners property, and it scares them, however he also states usually states knowing someone who knows someone, and that is a BIG help. As he said it makes it a LOT easier if you are NOT a complete stranger.
Offering to share finds is always a good idea, otherwise what incentive does a land owner have ? NONE. I always give. Like CRU said without land owners who "let you dig" what good is this hobby ? (with no place to dig, pretty much NONE)
Also as Bill said, if you want to dig on someone's lawn in town, and ZDD said better have a thick skin, and be preparred to hear, AND accept NOs.
Again it is NOT about "lines" it is about being a people person. Knowing people helps, start with people you know, then branch out, if your honest, and share, you'll probably do OK.