When I was pulling together our application, I also got asked a lot for what should they say in their letters and so I found on this forum somewhere an example of a request letter, giving them a bit of an idea of what to write, but of course, everyone has to say it in their own words.
This may be useful for you to copy and send out to your friends and family.
As you know I am seeking Permanent Residence Visa status in Canada through the Family Class immigration category. As part of the immigration application we are required to provide evidence that we are indeed a genuine couple and entered into a genuine marriage, not just so that I could live in Canada. This includes written correspondence, passport stamps from visits to see each other, plane ticket stubs, photos, etc.
An important part of this evidence of genuine coupledom/coupleship, whatever you want to call it, is documentation from family and friends. From reading Canadian immigration blogs it appears that the more documentary evidence we can provide from external sources the more likely our application will be approved swiftly, or at least not denied on this basis.
So I am writing today to ask if you would write an email on our behalf and send it to me by xxxxx. I realise this request is somewhat vague as to the content of the email, so I've included a list of basic points to cover at the bottom of this message. You are certainly welcome to write more, or less...whatever you are comfortable with putting in writing to support our Family Class application.
Please accept my heartfelt gratitude for your timely assistance in this matter, we both really appreciate it and just want it to go through as smoothly as possible.
Thanks so much.
General information to consider including in your message
1. A description of how you know either one of us (typically the person you knew first)...examples
I am a friend of XXX, I am the sister of XXX, etc
2. A description of how you became aware of our relationship, when you met the other partner, activities we participated in together, etc
3. A statement to the effect that, in your judgement, we are in a real, loving, ongoing, genuine (you choose the words) marriage based on your personal knowledge and experience