I recently moved from an iPhone to an Android phone. My immediate concern was how to move my contacts over between the two devices. iCloud backup of my contacts really came in handy for this.
First, make sure to have your contacts backed up to iCloud.
Log in to iCloud at https://www.icloud.com/ using your Apple ID and proceed to the contacts page. Select all of the contacts (CTRL+A for Windows, COMMAND+A for Mac), click the gear on the bottom left, and select export as vCard.
Now log in to your Google Contacts using your Google account. Click import and select the vCard file you just exported.
Upon completing the import, make sure to review your contacts and merge any duplicate contacts that may have resulted from the import. This is the perfect opportunity to clean up your contacts before syncing them with your phone.