You will need to use iCloud on your macbook and iOS device, with them you can manage the data from iCloud on your iPhone, iPad, or iPod touch. When syncing with your macbook, you can sync with the USB cable that came with your device, or over Wi-Fi when the macbook and iOS device are on the same Wi-Fi network. But transferring apps, photos, contacts and videos needs different operation, you can check that on apple?s support to get further information. Or just simply google iPhone to mac Transfer to get some useful tools.
Of course itunes will delete the old data if you sync your iphone with itunes! You should put your iphone on itunes manual management, which lets you drag and drop what you want onto your iphone without syncing. do as the following: Connect your iphone to computer and launch itunes--find iphone under the "Devices" category in the left panel-- check the "Summary" tab on the right-- click "Manually Manage" --"Apply". Well if you don?t wanna go through the troubles just get a iphone transfer to do all the backup thing.
for Windows:how to transfer contacts from iphone to PC