I am no designer, but I usually forget that and always get my hands dirty trying to do do some design. I believe design is at least 50% of an app, because of that I already lost the count on how many apps I bought just because of their beautiful design, it's like collecting paitings.

Over the years I gathered a few tools that help me when trying to create iOS apps, believe me, this will make your life a lot easier.

• Sketch: Imagine this, a tool designed for pixel perfect designs, that allow you to preview the design right in your phone. On top of that you can slice your design and export it with the correct sizes in one action. (link)
• Pixelmator: Indie developers don't have money to buy Photoshop. But that's not a problem, for my needs Pixelmator proved more than enough, and it's fast, much faster than Photoshop. (link)
• iOS GUI: This has all the default iOS elements so you can start prototyping your idea right away. The best part? It's already in the Sketch file format. (link)
• xScope: If you are a pixel perfect freak you will love this app. With this you can measure anything on your screen, magnify, insert guides and the list goes on. One of my favorite features is pick colors and save them to clipboard as UIColor declarations. (link)