One of the most important tools of your app marketing campaign (with or without paid acquisition) is Keyword Optimization (KWO). With it, you'll improve your keyword pool, i.e., the collection of words on your app's metadata that are scanned by search engines.
Choosing great keywords and key-phrases takes time, and you have to make a considerable list of words and phrases that are somehow related to your app. The list should have hundreds and thousands of key-phrases and keywords.
After you've brainstormed your list, it is time to filter the bad terms out and choose your final set of keywords. Pay attention and take your time to make a great selection. The keywords you choose will impact directly on your app’s exposure, downloads, and, therefore, revenue.
There are several methods out there to choose keywords. The one that worked best for me is the straightforward, three-step Relevance, Competition and Volume method, and I'll show you how you can do it and why you should do it.
If you have to learn one thing from reading this article, it's this: relevance is king. Period.
The single most important aspect to consider in keyword selection is relevance. Without relevance, you get no conversion, no matter how great your app, icon, screenshots, or video previews are.
Imagine the following situation: you search for a "golf assistant app" and the third app you see is an ice hockey game. Unless you love any sport that is about hitting balls with sticks—in that case, you should try baseball too, I heard it's awesome—you wouldn't download it.
People want to download what they are looking for. It's that simple.
And this is cool, because users who downloaded your app from the search results are usually after apps with the highest quality. They were looking for your app, after all. They just didn't know it yet.
Since you don't get downloads from keywords or key-phrases with no relation to your app, don't waste your time using them. Even if you do get them, user quality will be low: they won't engage or spend on your app.
So, how do you know a keyword is relevant? Basically, you will know if the keyword or key-phrase is relevant if it falls in one of the following categories:
Put yourself in the user's shoes: what am I expecting when searching for that key-phrase? Ask people if necessary, or Google it and analyze the results. Is your app related to the results?
After you boiled down your list to relevant keywords and key-phrases, you have to check the competition. Your goal here, after all, is for users to discover your app. However, for keywords with robust competition, you are not likely to appear in the first 10 or 20 positions in the search results, which is as far as most users are expected to go on iOS 8.
Evaluating competition is hard because it's relative to the strength of your app or marketing budget. If you're going barehanded in advertising, relying on App Store Optimization (ASO) alone, start by looking at keywords with weak competition. Make sure you'll rank high for them just with organic downloads. Look for apps with similar theme, functionality, or production values and see how they performed for this keyword or key-phrase.
If you're going to make a strong paid user acquisition campaign at launch, you can use keywords with stronger competition. If you think you can't rank among the top 10 apps for that keyword or key-phrase, cut it out. Don't hesitate. If people can't find your app through it, the key-phrase is worthless to you.
With this step, you will probably cut most of your keywords, leaving only key-phrases. It's hard on today's app store to find good keywords with low competition. That's not a problem, though, since there are a lot of good niches with key-phrases.
How do you check competition? The most obvious way is to look at some "competition" or "difficulty" data from the keyword research service you're using. I prefer to actually see the apps myself, just to be sure.
Search the App Store for each keyword and key-phrase you're aiming for. Look at the top 10 apps and ask yourself these questions:
After you have come up with relevant key-phrases with competition you can handle, choose the ones with the largest traffic/search volume. Look at Google Trends, Google Keyword Planner, or your favorite App Store Optimization tool; all of them have data for search volume.
Choose the top one or two key-phrases and try to place them in your App Name, since it has more weight in the search results ranking algorithm, and you will rank higher for it. But do it in a way that your app name makes sense when reading it. A keyword-stuffed looking name, like “Adventure Candy King: Clash of the Titan Clans – Amazing Puzzle Power Magic Game with Golden Hero”, will probably get your app rejected by Apple.
Remember: this step has the lowest priority. Don't look at search volume until you have filtered your list by relevance and competition.
After you've chosen all key-phrases and keywords you want to use, you're ready to place them in the app's metadata. The search engine looks for keywords on the App Name, Keywords, In-App Purchase Display Name, and Publisher Name fields. You're probably too late for the last one, but distribute your keyphrases among the rest of them.
Pay attention to how you're allocating the keywords used in key-phrases. If you don't know how to do it, read this guide and understand how key-phrases work on the App Store.
In a nutshell, Keyword Optimization is Relevance, Competition, and Traffic, in that order.
Keyword research takes time, so don't rush through filtering and choosing or your work could go to waste. This is something that will directly influence your download numbers, so take your time and do it right.
If you're working with paid acquisition through ad campaigns, you might want to read this article to understand how Keyword Optimization and, therefore, App Store Optimization, can drive your effective cost per install (eCPI) down.
This is just my favorite method for choosing keywords, though. What other methods do you use to choose keywords?