Read emails, draft contracts, talk to somebody trying to buy or sell my client’s company, think about business structures, think about compliance issues, issue-spot and refer people to specialists in things like tax.
If you are a really big firm, you’re going to be very expensive and people will only come to you for really big things where they are betting the farm. That is where you find (generally) the country’s leading lawyers in mergers and acquisitions, competition law, national security, mining, securities, etc. those people are, in a sense, also corporate lawyers.