First, well done on getting that call!
Second, don't be nervous and try to be yourself as much as possible!
Third, remember you probably have a 5-10% chance of referral (at most) regardless of what you do...don't beat yourself up if you don't get a referral from them.
I have the following tips:
Ask For Yourself
While an informational call is a way for you to make a good impression, please remember that it's also about you making sure this job + path are right for you!
To prepare, think about things you'd like to learn about the company. Ask about your person's experience at the firm, where they've come from, if they have any advice for you etc. Be inquisitive and interested in what they have to say, and feel free to ask thoughtful follow-up questions.
Most importantly, remember this is a conversation! Keep it dynamic, two-way, etc.
Have Your Pitch Ready
In terms of what they'll ask you, make sure you have your 30 second pitch prepared! Who are you in a nutshell and why are you interested in Bain and strategy consulting?
Ask About Them
People love to talk about themselves. Just ask them what they've worked on recently or what their journey at BCG has been like. Importantly, do your research beforehand - find out what they've done and try and pick something from their past that looks interesting to you. Tailor your questions just like they tailor their FIT questions to your resume.
"So, how did you end up in the Industrial Goods sector?" "I saw you worked on a big digital transformation for a financial services company - I experienced one myself and it seemed so hard to move such a big organisation. What did you see as the major challenges and breakthrough moments?"
GENERAL NETWORKING TIPS
a) Reach out to people in your network
b) Reach out to people once removed from your network
c) Reach out to people with a similar backgorund to you (i.e. same alma mater, same historically underrepresented demographic i.e. gender, orientation, ethnicity, etc., same career switch, etc.)
d) Tailor a message to them specifically both showing interest in them and their journey and demonstrating that you have done your research and could be a valuable hire
e) Play "tag" across calls you get so that you can work your way towards the company/office/role you want
f) Never directly ask for a referral, but "hint" at needing one (this is nuanced and important...happy to talk through wording)