Wow Barrie, thanks for that, I think you have covered everything that I had wondered about (and that i have been doing wrong). I have had a look at online tutorials before tryiing all this and they make it seem so easy but do not describe in detail how you do it correctly (for example, not starting the cut over the edge of the glass). I will have to retry glass cutting with all this in mind and with a new glass cutter.
through different trials, I have tried thinsg like scribing both sides, scribing over an existign scribe, tappi9ng on the scribed side, tapping on tehg non scribed side, using oil (cookign oil though), using the khooks/notches on nteh cutter to try to break try glass and loths of others....The one thing which I do remember trying (and thought it would work / was smart) was to use a hair dryer to heat the scribed area in hope that5\ it woulkd slowly create that stress on teh scribe and crack it correctly... didnt work either :-(
Thanks for such a good writeup, will give it another go when I have more glass
Matt