Samuel this is a brilliant question and hopefully you get some useful answers. In my experience with podcasting this is the biggest challenge on assumption you're wanting people to actually hear what you've produced.
I've had mixed success with building a podcast audience. I've never hit the 'big time' with 10's of thousands of listeners but I've had a podcast where around 1000 people listened each fortnight and a lot of them were actively engaged. That was because it was a niche podcast - in this case it was a gaming podcast devoted to a new MMO game and we started the podcast to build interest BEFORE the game launched. We ended up running that podcast for more than 140 episodes although the audience had depleted substantially, mostly because I expanded to podcast coverage beyond that one game. This seems like a good move at the time but it was the beginning of the end: it was no just one of thousands of gaming podcasts out there.
Now with marketing, I find it requires money that you need to spend before there's any chance of the podcast generating revenue (if it ever does). So that means PAID advertising on social media, building a presence on Twitter / FB / Instagram etc. Even then there's obviously no guarantees sadly