my advice....
understand YOUR processing office... what is gospel for one, may be irrelevant to another... (for example, Kingston Jamaica near ALWAYS requests original birth certificates from the applicant and marriage certificates.).... also know what your office usually considers red flags... find out why the people who have been called for an interview were called and what questions were asked... knowing these things and preparing your application to proactively address concerns that are common will put your application one step ahead...
also, more doesn't always equal better in most cases... unless you know of a fact that the office takes a file's weight into consideration when evaluating (and apparently some do, again, know your office), then don't take 500 pages to say exactly what you can say in 50.... Many VOs will appreciate a well organized, well presented, consise application over one that has included everything but the kitchen sink in hopes of overwhelming them in information... think about it... which file would you rather jump into on a dreary Monday morning? make their jobs easy and they will repay the favour...
suggestions to do this... instead of including 100 pages of chat, 100 pages of phone records, 100 pages of emails, include 2-3 pages of each (maybe 3 "sample" days of your relationship, one from early, one from middle and one from recent) and provide the quick explaination that there are 300 more pages that you can present on request....
also once you're pretty sure your evidence is solid and you've addressed any concerns the VO will have, make it presentable! use tabs and section things logically, use simple direct language and don't get overly detailed where it's not necessary... maybe use graphical representations (timelines, maps ect), anything that will avoid your application being a long winded story that will turn the VO glossyeyed while reading... get creative without going over the top... while what you say is important, how you say it can also work to your advantage... make it easy to understand and not something that they will have to read 5 or 6 times just to get it... the easier it is for the VO to paint the picture of your relationship in their minds, the more they will believe in it... and if they believe it, they will make it happen for you...
just my thoughts!