Is your iPhone or iPad feeling a bit sluggish? Has it lost that snappiness that it had when it was new?
Here's the simplest way that I know of to speed up an iPhone or iPad.
Wipe the device and reload your data from a backup.
Yes, it really is that simple.
I tend to do this every year for my devices, and not only do I find that I have more free space available (because app caches aren't part of the backup) but the system feels snappier and more responsive.
I also take this opportunity to delete apps that I no longer use, freeing up more space.
But before you do anything, first MAKE SURE YOU HAVE A BACKUP! That backup can either be up on iCloud or you can do one using iTunes. If you wipe your iPhone and you don't have a backup then you're going to have to reload your apps and information manually, and that's going to take you a lot longer than recovering from a backup.
The wipe process is easy to carry out: