With my family and friend, we gave them a small outline as to what they might want write about, including things we did need them to write (their full name, address, relationship to sponsor or applicant, basic important declaration stuff). Things like on when they became aware of my fiance and I's relationship, how we met, etc. How they met my fiance face to face first time, where, activities we did. Then they could each write about their personal opinions on our relationship and if they agreed to the genuine nature of it (all did of course). Each of them included their testimony to my fiance and I having lived together for more than 1 year (3 to be precise). There's really only a few basic things they need to write. If they are personally familiar with you and your partner and your relationship is genuine, they will all agree unanimously.