Secret performance fixes: How to speed up iPhone slow!

Whether you're still worried about updating to iOS 8 on your iPhone 4s, or you simply want to make sure your brand-new iPhone 6 or iPhone 6 Plus stays as quick as the day you bought it, here's how to both reverse slow down and maintain speed.

Note: We're staging these from easier to most involved. Go through the list, try each one in turn, and do as many as you feel comfortable with. The older your iPhone, the more you'll likely have to do.