As an iOS developer it behooves you to learn about marketing on the app store. Not only as a service to your clients but to protect your own reputation. If there's one thing I see in my own business it is a lack of money and time invested in marketing. Yes the app store has a massive user base but it also has a massive amount of apps on it. Consider this graph on the cost to acquire 1 loyal app user from Fiksu the worlds leader in app marketing.
Pretty sobering numbers and just look at their client list; Zynga, Coke, Paypal, Disney. If huge names like these are coming to them for help it must be a tough market.
##How to help your clients and yourself##
Despite huge competition and massive marketing budgets for corporate giants there's still plenty you can do. Here are a few suggestions to get you started.
1. Build a user base before you build your app - Get your clients to start connecting with potential customers on social networks, forums and their own websites as soon as you can. When your app launches you want a fan base ready and waiting for it. One of the biggest reasons projects on Kickstarter fail is the "build it and they will come mentality". It's just not true, you need to launch with an audience and user base already created. They'll get you started and build you momentum to pick up new users.
2. Pick a niche - The clearer you can get about who your customer is the greater your chance for success. Niches help you define this and it makes finding these people far more easy. Consider this example. Pretend your client wants to create a social networking app. Where do you start looking for users? The answer is everywhere and no where. However lets consider creating a social network for people who love Teacup Chihuahua's. It's all of a sudden become a lot clearer, you could post signs in pet shops, advertise in breeder forums, use Google adwords and target people looking for specialty dog food for extremely small breeds.
3. Make sure your're solving a problem - This may be getting a little out of your scope as a developer but consider this. When you're writing your use case scenarios for an app designed to generate a random smiley face each time you shake it, ask yourself if you're solving someones problem. Chances are if you answer no, it's time to counsel the client or maybe leave the job to someone else.
For some smart reading on mobile app marketing and more useful charts you can use with clients I recommend visiting Fiksu's Blog.