I like to write small (~$1000) checks in friends' companies. I'm pretty sector agnostic; I really just believe in my friends and think they're likely to build great companies! Here's what I've done so far:
I've always been venture-capital-curious but am strongly convinced it's the wrong full time job for me, for now. VC feels like a great "late career" thing, much like being an academic (see Fred Turner or Nathan Schneider, both first journalists) or being a journalist (see Matt Levine) is often best with some other experience first. I think I have a more valuable perspective on what software companies will buy spending more time working in startups, have deeper domain knowledge, and meet more people likely to start companies.
This said, I think it's most interesting to see the startup ecosystem from several different vantages; playing each role lends a more accurate perspective. There's a very interesting vision of the startup ecosystem that seems a key role in the superconnector / network-entrepreneur type, i.e. someone who can pair an idea with founders, founders with engineers and capital, and profit from the whole transaction. Andreessen Horowitz is actually modeled after the talent agency CAA which does this sort of "packaging" approach in Hollywood. A sidenote that Michael Ovitz's memoir is one of my favorite business reads of the last few years.