I'm looking for some help with the following. This will be a very general and vague question but i would appreciate people's input.

I'm currently learning Objective-C with the idea of developing applications for iOS. So far it is going ok - i'm obviously starting at the bottom, "Hello World", adding two numbers etc. Next i'm going to be making my own calculator.

Other technologies i'm familiar with are HTML5 and CSS3. As far as JavaScript goes, i have used it for form validation, not much else. I have been introduced to the idea of AJAX and JSON. I have used PHP for server-side form validation and formatting and sending contact form information, but not much else. I have almost no experience with MySQL.

I guess i'm looking for people to tell me what i need to know! Are there recurring actions that come up when developing an application? If so, i want to practice these. For instance, is setting up some kind of user information database a common action in application development? I don't know how to this but if it is common i want to know how.

I don't know if i'm making myself clear, but i'm looking for the real basics here. "Often when developing an application, people will need to do x, y, z so that they can do a, b and c".

I'd really appreciate any help with this, as vague and simple as it may seem.