Odd that youve never had luck with it before? maybe the way your doing it, cause i take cut off all my tomato's in spring from the bottom 6 inch so that i can sink them deep into my pots so the wind dont knock them down and they get big and thick. but i save all the cuts outta every 10 i make i may have 1 or 2 not make it, but i just make a mix of potting soil, peat moss a small amount of bark mulch and push the cut into it and pack the dirt around them down a little and keep them good and wet, first couple days they droop. usually they come back, if not they go yellow and the current leaves fall off but they regrow new ones, their just a bit slower then if it takes a good root right off the start and dont end up going yellow. Last fall i cut the main head off two of my roma tomatoes and cloned the tops and nursed them all winter indoors then put them out this spring, their my two largest plants, only been outside a few weeks now and their already pushing 3 feet. and stalks are over a inch thick at the base. 30 or so tomatoes on each, did a blog about it a few days ago.