Detailing his how he came to his findings, Zarella says:
Using a dataset now more than 1.2-million tweets strong, I found two particularly impactful characters, which when present in tweets tend to correlate with those tweets being more likely to be retweeted: quotes and hashtags.
The results of the research suggest that tweets containing one or more hashtags are 55% more likely to be retweeted than tweets that do not. It’s unclear at what number of hashtags are too many, but we’d suggest that it’s fairly easy to slip from hashtags being helpful to annoying for your followers.
Tweets including quotes meanwhile will give you 30% more retweets than those that don’t. Zarella doesn’t say why this is, although we’d suggest that it might be down to the fact that when people use quotes, they’re frequently reporting what’s been said by voices of authority.