It's hard to know where we started seriously advocating a move to Clojure and where it was just our enthusiasm but we did quite a few things to sell it.
- A Clojure club where we booked a big meeting room and taught some of the basics of Clojure
- Buying a bunch of books and leaving them around the office
- Re-writing an existing service into Clojure as an example of how quick this was to do, and how nice the resulting code was (as a note we haven't gone back to re-write working services)
- High levels of enthusiasm and trying our best to make sure everyone got a chance to be included
At some point we decided that we had enough support to try things more seriously so we got all the devs together in a room and made a proposal to work on a few new services in Clojure. Having a Service Oriented Architecture actually really helps here as we didn't have to make too big of a bet. That was enthusiastically accepted by the team and from there we ended up writing more and more things in Clojure. A few people were more resistant than others and they stuck working on Java projects for longer. After a while though curiosity or necessity led to them working with Clojure and they ended up convinced. I'm not aware of anyone now who isn't a fan.
Training was a combination of self taught, books and, later on, booking a 3 day, onsite training course from the guys at Lambda Next. This is something Cognitect also offer now.
From a dev ops perspective not much had to happen as our existing Java tooling continued to work. That said we have recently rewritten all our deployment tooling (in Clojure) to target AWS (and generally improve it in just about every way). We actually have a blog post due to be published this week talking about our new, Clojure based, tooling.