Sync iPhone

Your best bet to keep iPhone Contacts, Calendars and Notes synchronized with Gmail is to use Google Sync
Let's start with Contacts

Before attempting the follwing procedure, for more safety, please consider our tutorial
Backup iPhone Contacts

Sync iPhone with Google Contacts

• On your iPhone, go to Settings->Mail, Contacts, Calendars->Add Account->Microsoft Exchange
• Fill the 4 required fields as follows:
• Email: your Gmail address, for example your.name@gmail.com
• Domain: [ Leave this blank ]
• Username: your Gmail address again
• Password: your password for this Gmail account
• Tap "Next"
• A new field called "Server" appears. Fill it as follows:
• Server: m.google.com
• Tap "Next" again
• Select the Google services ( Mail, Contacts, Calendars ) you wish to sync
• Tap "Done"
• Tap "Keep on my iPhone", so that your existing iPhone Contacts and Calendars are preserved

Sync iPhone with Google Calendar

Unlike for Outlook, setting up iPhone Calendar to sync with Google Calendar isn't that simple, particularly when trying to perform this without any additional software

This tutorial provides a simple solution that works without installing any third party application

• On your iPhone, go to Settings->Mail, Contacts, Calendars->Add Account->Other->Add CalDAV Account
• Fill the 4 required fields as follows:
• Server: www.google.com
• Username: your email address, for example your.name@gmail.com
• Password: your password for this email account
• Description: Google Calendar
• Hit "Next" and you should be all set

Notes & possible issues

• iPhone 4 users: your iPhone Notes will show up in your Gmail Account with the "Notes" label
• Refer to this tutorial to Transfer existing iPhone Notes to Gmail
• Once the above procedure is completed, your iPhone will synchronize with Google Calendars every time you connect your iPhone to your Computer
• Your iPhone system must be 3.0 or above
  To check your current iPhone version, go to Settings->General->About->Version
  If you need to update your iPhone firmware, just follow these instructions
• In case of any iPhone Contacts synchronization problems. On your iPhone go to Settings->Safari->Clear Cookies and restart the Contacts application ( if your iPhone supports multi-tasking, make sure you have actually closed the Contacts app )
• Depending on your iPhone version, some characters in the password may cause problems to set up a CalDAV account ( typically "#" and white spaces )
• If Gmail keeps asking for your Exchange password, the problem is that you don’t see the captcha. Visit this page to see and unlock the captcha
• If your iPhone Calendar events don't show up in your Gmail Calendar, make sure to set your Gmail account as your default Calendar (Settings -> Mail, Contacts, Calendars -> Scroll down to the Calendars section and under Default Calendar, choose Gmail)
  If the problem remains, edit your Calendar settings for each of your events (Select an event, click Edit, Scroll down and click Calendar, under Exchange select Gmail, hit Done twice)
• This solution allows to sync Gmail contacts with iPhone 4 and iPhone 4S