One of my favorite topics to research is ReTweeting. I have several very large (millions and hundreds of millions of rows) datasets that I use to do my analysis. The results of my research with these databases are best practices, generated across many industries, timezones, account types and languages. This data is a great starting point for your experimentation.
The best data is always your data. So I created a free tool, ReTweetLab that allows you to do the same kind of analysis that I conduct on my large datasets on your account (or any other Twitter account you want).
For each criteria ReTweetLab analyzes, it shows you two things: what you’re currently doing (the small chart in the text) and the effect that criteria has on you getting more retweets (the larger graph below the text). In the example above, we see that the vast majority of my Tweets do not contain hashtags, but those that do tend to get more retweets.
In this example we see that the average @JetBlue tweet is just over 100 characters, while shorter tweets (more like 50 characters) get the most retweets.
So go, check out ReTweetLab and see what results you get.