How should I decline an offer from grad school I know such type of questions has been asked lots of times, but I do believe people's conditions vary and there is not necessarily someone who has an identical condition to mine, so please allow me to ask such question again with some details.

I was applying for master's degree in computer science, and got accepted by the one that I've accepted and the other one that I have to turn down now. It was the professor who contacted me first, and one month after I received my offer, I went to the city and visited the school and met professor in person. We talked about a number of things including the research, her supervision style and such. However, I don't think I ever speak like I will for sure go to that university, as I pretty much kept myself conservative. Now I've made up my mind to attend the first school already, so I want to know:


Should I send an email to the professor, besides one to the admission office, that I am about the decline the offer?
If yes, what content should be included in the email? How long should that be? Should I explain carefully my reasoning of picking school?


I well understand that it needs to be extremely polite, but other than that, I am not very sure what to mention.

Also, it would be nice if you can share some experience you have in general when you turn down your offers.

If it helps, I applied to schools in Canada, but I also welcome experiences in the US.
I am a professor and have experienced this situation from that point of view. Any experienced professor should be used to that, I would not worry too much about this.

I would suggest writing a brief mail to the professor to just inform her that you have accepted another offer. She might be interested to know what offer you accepted, so consider informing her about that, but you should not need to defend your decision.