Slow iPhone 3G - some things to try

If you have an iPhone 3G, it may have slowed down a lot with the mandatory software update iOS 4.0. These are some things that potentially could improve performance and/or battery life. It may not help, but it does not hurt trying.

1. Upgrade to 4.0.1.
2. Delete superfluous data (big movies, applications, photos) to make sure the phone is not full to the brink.
3. Disable international keyboards you do not use, in case you activated them.
   
4. Switch off 3G. Preferences > General > Network.
5. Switch off location services. Preferences > General > Location Services.
6. Switch off Push notifications. Preferences > Notifications.
7. Switch off Spotlight Search. Preferences > General > Home Button > Spotlight Search. Unselect some or all.
8. Do not use Folders.
9. Restart. Press and hold both the Sleep/Wake button and the Home button for at least ten seconds, until the Apple logo appears.

And then some things that may hurt, as some of your data will be deleted:

1. Reset the phone. Preferences > General > Reset. Choose which items you want to reset.
2. Restore the phone to factory settings. In iTunes, the tab Summary, click on Restore. http://support.apple.com/kb/HT3828
   
3. Downgrade to iOS 3. I would not dare doing this myself, and do not know how to do it. However, you should be able to find instructions elsewhere if you search for it. Apple does not currently support this.

Update September 2010: But first, upgrade to iOS 4.1 which apparently solves a lot of problems.