A personal note is important and means a lot, even if it’s just a few words. I usually begin with “Please accept my heartfelt…” or “Let me be one among many friends who…”
If I knew the deceased well but not the family, I say something about why the person was special to me, maybe mentioning some specific memory: “I’ll always remember the way she laughed,” “I’ll never forget the time we…,” “He was the greatest teacher I ever had.”
If I didn’t know the deceased, I focus my message on the person I’m sending it to: “It’s so hard to lose someone you love. Take the time to grieve, but hold onto the wonderful memories.”
Having lost both parents and received a lot of cards and floral tributes, I can say that the least polished-sounding messages sometimes mean the most because they come from the heart.