What is the best way to wire ceiling lights?

With real fault finding you have no idea what the wiring style is until afterwards, only that something is not right,  and actually in anything that is not a brand new house, you have to assume it may well be a hybrid of a bit of this and a bit of that and using every system known to man used in different areas.  If for example a light is not working, it is not even obvious what circuit it is on. (I have found a house where the upstairs lights, all of them, plugged into a socket hidden behind a wardrobe, the neatly labelled 'upstairs lights' fuse did nothing - I presume it was a temporary fix in the middle of some building work, and the chap or chappess never came back to finish the cable run, after all 1mm T and E is not a great fit in a 13A plug.)

Visit a friends house and try and guess the wiring routes and methods by what you can see. That is all we can do.

There may well be surewire or other JBs or even choc bloc or tape and twist joints buried in unreachable parts of the installation that did not seem to be part of the problem. Even when you leave it is quite likely you will still not know for sure if there are joins in the parts you did not dismantle, though you may suspect, if there are clues such as the wires at the switches are 1mm and white jacketed and the wires at the fitting are 1.5mm and grey.

Often though it is not that obvious, and sometimes it is better if a whole branch of unexplained mystery is cut-off and abandoned as beyond economic investigation and possibly non-compliant, and a new wire routed to get a supply to the load by another route and an obvious wiring method. Novel methods just confuse inspectors and repairers, and in some cases the original installers as well.

With real fault finding you have no idea what the wiring style is until afterwards, only that something is not right,  and actually in anything that is not a brand new house, you have to assume it may well be a hybrid of a bit of this and a bit of that and using every system known to man used in different areas.  If for example a light is not working, it is not even obvious what circuit it is on. (I have found a house where the upstairs lights, all of them, plugged into a socket hidden behind a wardrobe, the neatly labelled 'upstairs lights' fuse did nothing - I presume it was a temporary fix in the middle of some building work, and the chap or chappess never came back to finish the cable run, after all 1mm T and E is not a great fit in a 13A plug.)

Visit a friends house and try and guess the wiring routes and methods by what you can see. That is all we can do.

There may well be surewire or other JBs or even choc bloc or tape and twist joints buried in unreachable parts of the installation that did not seem to be part of the problem. Even when you leave it is quite likely you will still not know for sure if there are joins in the parts you did not dismantle, though you may suspect, if there are clues such as the wires at the switches are 1mm and white jacketed and the wires at the fitting are 1.5mm and grey.

Often though it is not that obvious, and sometimes it is better if a whole branch of unexplained mystery is cut-off and abandoned as beyond economic investigation and possibly non-compliant, and a new wire routed to get a supply to the load by another route and an obvious wiring method. Novel methods just confuse inspectors and repairers, and in some cases the original installers as well.