I don't think we wrote more than a paragraph or so about how we met, but we made a timeline with significant events covering the entire length of our relationship (including visits, dates of ceremonies, the date he proposed, anything else that might affect our relationship/decision-making processes, etc.). The timeline ended up pretty long. When writing about our ceremonies (we had one in Canada and one in the US), I don't think I was very detailed about the ceremonies themselves, but I did explain to the best of my ability why my family didn't attend the ceremony in Canada and why his didn't attend the ceremony in the US. And we included a few pictures of each ceremony in the description (with I think more pictures from the ceremonies included in the section where we included supporting evidence/pictures from visits).
I suppose you will want to balance ease of reading with thoroughness.
You may want to take a look at http://www.canadavisa.com/canada-immigration-discussion-board/how-i-organized-our-applcation-and-a-summary-of-all-helpful-tips-i-have-learned-t92449.0.html to see how this person organized their application. There are probably many right/acceptable ways to organize an application (and if you asked, people would probably all give different answers), but if you plan ahead and have an idea how you're going to put it all together, it might make it easier and more efficient.
