I notice in the forum there are some articles related to naturalization. Th experiences seem to differ widely so I will simply add my experience as a possible exemplar of how things currently are.
I applied for Facilitated (via marriage) Naturalization in Kanton Schaffhausen. At the time of application I had held a "C" permit for about 18 years and had lived in SH (and had been married to a Swiss national) for just over 3 years. I applied 1Q 2017.
Very soon after, within a few weeks, Bern requested many original copies of many documents, some from the UK and some from Switzerland. The Swiss forms were produced very quickly so within a month of receiving their document request my, I had everything Bern needed and sent it all off.
All goes quiet for just over a month and then am contacted by SH Police to attend my formal interview. I think this is the part of blog most people will be interested in.
I turned up at the police station on time (of an evening), but first I did partake of some dutch courage to calm the nerves. Everything was in German and for sure if you could not hold your own at a basic conversational level in German then it would have been a very short interview.
The policeman was a good guy, thorough and fair. He asked at the beginning should he speak High German or should he use the local SH dialect. I had lived for over 20 years in Zürich so asked (as a joke) if we could speak in the ZH dialect. He laughed and declined. So I opted for SH Deutsch and hoped for the best. I think it is best to opt for the local dialect. You lose no points at all for not being able to speak the local dialect and even if you have difficulty in understanding it, I got the impression he would have taken off some of the dialect if he thought I was struggling. As I say, a fair guy with a fair view.
We chatted about quite a lot of stuff. Nothing was asked about Kantonial or National history, traditions, geography etc. basically he was interested to who I was as a person and my motivations for becoming Swiss. I was actually a bit annoyed about the lack of "Swiss" questions as I actually knew a fair bit about Switzerland and, like everybody else, had done a fair bit of homework too .
The overriding element of the interview from my experience is to simply be honest. Do not try and create an image of who you want the interviewer to think you are. Disagree with the interviewer if you feel so inclined and put your point of view across. Being able to express your view I sensed was important. Oh, I was asked did I have a formal German language qualification and I did not. However from example tests on the internet I said I was absolutely minimum B1 and was 90% B2.
After the interview then the big begins. Everything goes into a black hole and I heard nothing for about 9 months.
I then received a letter asking me to show evidence that my Wife and I had been and still were in a genuine marriage. I was also asked to tell them anything I had done/do to show I am integrated into Swiss society. Marriage proof was in the form of a zillion photos of holidays, plus associated flight and hotel booking confirmations which showed my Wife and I had traveled continuously, as a couple, since we were married. This was easy as we travel a lot and have loads of photos. The second request for proof if integration cam from my side in the form of references for a club I was in, a center I help out at, and photos of my Schrebergarten. I work in Zurich so with travel to and from the office, I personally do not have many free hours Mon - Fri so I did worry they may have been disappointed at my examples of integration, but once again, be honest and just tell them what you do. I did mention my long work days during my interview so it was on file that there was not much time for much more in my life just now.
Sent all the "proof" off, then waited again. 2 months later I then received a very formal form requiring me to answer questions relating to whether I had ever had undertaken anything which broke Swiss law and whether there were currently outstanding criminal proceedings against me. What I would say here is that if you have ever had any formal dealings with the Police, simply go to the police station and ask them how you should answer the specific questions. Speak directly to any police officer you may have had dealings with ans ask them personally. Basically, be honest but ask advice if you have ever had Police matters.
Sent off the form then waited about 2 months and received a letter saying that everything was positive and that I must wait, up to 2 months, for the Kantons I am associated with (where I had lived in the past 5 years and Kantons (Heimatorten) associated with my Wife) to possibly raise an objection.
Within 6 weeks I was informed that no objections has been raised and I was now formally Swiss. It then takes about a week or so for my new Heimatorten to acknowledge they have been informed that I am now on their registers. Once I had this form, I could simply apply for an ID card and a passport, both of which took place within 3 days.
Basically the process is a bit lengthy, but is thorough and fair. Do learn the language of your Kanton, in particular listen to radio etc from your local area so as to get your ear tuned to the dialect. Do learn how to speak the "high" version of the local language.
Above all "be honest" and be yourself.