Having recently read a post by someone who was frustrated that they weren't getting any reviews of their podcast, I started thinking about what the selection criteria are that lead me to listen and then knock out a post. Below I've put together a list of a few things that make it more likely I'll look at a podcast, which you may want to take on board if you're hoping other people will do you a review. Obviously, these are just me. Other people may be different, but I would bet there are some overlaps.
Disclaimer: I have never made a podcast. I've just listened to a few too many.
1. Amount of content
At the moment, I mostly listen to long-form audio drama. I'll pick up anthology shows occasionally (currently attacking the No Sleep podcast prior to podUK), but let's assume I'm always listening to audio dramas that are episodic with an overarching plot. That means I need to listen to enough to get some idea of what's going on and where it's going. I'll also want to have formed an opinion about the quality of the production, whether the characters are well-rounded, and how much fun I'm having listening to it. I'm not the most literary of "critics", and really, my main concern is whether I find something enjoyable.
Secret squirrel fact: "enough" is a variable characteristic. My preference is to listen to the entire first series of something, which usually equates to 1.5 - 4 hours, though that can stretch to more in some cases (side-eye at The Magnus Archives). A minimum of a couple of hours is reasonable, I'd say. This means you need that level of content to expect someone to do you a nice post. People aren't likely to review a trailer. Feel free to let people know about it straight away, though. They can always start listening with everyone else, and there are a few newsletters floating about.
2. Ease of access
At this point, there's many ways of getting podcasts. The oldest (and my preferred) method is directly through an rss reader, which means all I need to hear your work is a link to an rss feed and my mp3 player. However, other people might use iTunes, Pocket Casts, Overcast or a whole bunch of other things. Make sure you can get to your podcast on all of them. (Unless you're paywalling it, in which case I've got no idea.) Make that rss feed as obvious as possible.
Additionally to that, get a website. You want people to be able to google the name of your show and find you, and the information you'd like them to see. This can be more easily shared than almost any other format, and you can also self-host the mp3 files rather than using one of the specialised podcast hosting services. A "click to play" feature on your site is another way of getting people impulse listening.
On the subject of googling, do yourself a favour and carefully consider whether you really want to name your podcast a common phrase or single word. Most people will think to add the word "podcast" to their Google searches, but it can still be difficult even then. Do a quick search on your intended name to see if anyone is using anything close to it. In some cases, I've discovered two podcasts, one called "[Noun]" and one called "[Noun] Podcast". I wanted the former. I kept finding the latter.
I also suggest putting your title in Urban Dictionary. Just in case.
The thing that prompted all this was an audio drama hosted on Youtube. It's a desirable option for some people, costing no money (useful when you're a new creator just starting out), and allowing the usual ad monetization. However, in my opinion only using Youtube is a terrible idea. It's getting harder to use on a phone if you're not prepared to pay for the premium, with it pausing itself when you lock the screen and so on, and it makes it irritating for a sound-based medium. Don't use it as your only (or even main) distribution system. It will not go well.
Why should people listen to your podcast and not the one next to it? You need to give them something that will grab their attention. As a bare minimum, you need a punchy synopsis, that tells people genre, type of podcast (anthology/ongoing), and a short plot description. Also worth throwing in any elements that make it appeal to a particular demographic, eg if it's an "own voices" podcast.
Next, you want images. A good cover image will do wonders for attracting people through the busy shelves of a stuffed podcast store. Those are mainly square, I assume because iTunes wanted to just reuse their album code, but a few different sizes don't hurt. (I use 960x540 if you wanted to make my life easier.) This will give people something to stick in tweets or facebook statuses, which does help with the eye grabs. Be sneaky, and make one big image that you can cut down to a few different aspect ratios without losing any of the important content. Now everybody can use it.
And finally, you might want a trailer. Now I confess, when I first considered this, I wasn't too sure of the idea. If I see a podcast, and its feed has a trailer and an Episode 1, I'm jumping straight to the first episode. My time isn't so precious that I can't spend the twenty minutes to have a listen to something completely new, especially if I combine it with the washing up. Further thought on this has convinced me of the benefits however.
I'd say don't make the trailer first. It should be assembled after recording a few episodes, so you can take a "best bits" approach to it. Then you want it to be easily listenable. This is where Youtube works. (Other video sharing sites are available.) Combine it with some pretty images, and it becomes immediately shareable through Twitter, Facebook or whatever you like, and people are more likely to spend the short amount of time it takes to have a listen as they flick through.
Even better if you can get it onto another, already popular podcast. I suspect people are less hostile to adverts for other podcasts than for more ruddy mattresses or meals in boxes. Aim for something in the same genre as yours. It's a ready-built audience. If you're two small podcasts, maybe you could do a swap.
It is very important that any trailer placement isn't obnoxious. Now, this is a taste thing, and it works on a personal scale. For me, breaking up the flow of the story by sticking it anywhere between the title and the credits is the worst.
You've made an amazing podcast. You've got a few hours of outstanding audio, it's available on every distribution method you can think of, and you've put together enough of an introductory info pack that when people see it, they'll definitely want to have a listen. The problem now, how do you get people to see it?
Here's where my advice will be very coloured by what I listen to and how I find them.
Firstly, Twitter. I've become a bit obsessed, and there are a couple of hashtags that I follow pretty closely. The first is #AudioDramaSunday, which people frequently use to share either their work or others they recommend. Then there's #PodernFamily, which is good for talking about/to other podcasters. And it's always worth considering tagging in your genre or your preferred method of spelling your #joineduptitle. See if you can set the trend for it before other people do. (Also, also, make sure that when you run your title together into a single word, you can't spell anything dirty. Unless you're into that.)
Fair warning, some people really overuse them, such that they appear a disproportionately large amount. That is a wonderful way of getting yourself muted. Don't be annoying.
Next, public forums. Since the old Audio Drama Talk disappeared years ago, I've moved across to Reddit. r/AudioDrama is a nice community that happily takes self-promotion (within reason) and is an excellent place to find really committed listeners for your work. There are a couple of other places that take this sort of submission. Give it a google. I won't namedrop anyone directly until they tell me they're happy for me to. (If you want adding to a list of reviewers, contact me and I can probably throw a page together.)
Finally, there's direct outreach. If you watch twitter long enough, or search something like #audiodrama review, you'll likely find people who post reviews. The same also applies to the subreddit I mention above. It is permissible to approach those people unless they don't want you to. If you can, consider dropping them an email with a direct link to the relevant mp3 files along with some sort of press kit. The synopsis, pictures, trailer etc from above, with maybe a couple of bios if you want to and all the relevant web links. Don't make them go hunting for the necessary info.
Now, there's an etiquette for this. Firstly, if they have review submission guidelines, follow them. (That means looking at their website if they have one.) It makes your chances of success significantly greater. Secondly, they don't owe you a review. Accept a "no" gracefully. Burn no bridges. Thirdly, don't be afraid to follow up if you get no answer. Single follow up, a minimum of a week later. Don't do it again after that. Being ignored is your answer. (Keep an Excel sheet of your contacts. Nothing like emailing the same person twice with your stock opening template.) If you're approaching someone via Twitter or Reddit, the only method of approaching might be DMs, but do due diligence and see if you can determine if they want to be contacted first.
And if they don't like your work, I'm afraid that's just the subjective nature of art for you. They might give you a simple "sorry, not for me", which you should not try and argue with. Pester someone enough with "but why don't you like it?" questions, and they might just publish that negative review a bit more aggressively than they otherwise would. Definitely don't sit in their comments shouting at them. It's all PR.
Probably the best source of favourable reviews though is your fans. Interact with them. It's likely you already are, given that's how these things work now, but find the ones who are really keen, and suggest they might want to share their enthusiasm for your work. Have a press page on the website you now definitely have. Have links to the relevant review submission pages.
Right, I think that's me waffled on long enough. This may or may not have been useful. Feel free to pass on your own tips in the comments, or tell me how I'm completely wrong.