I've had to do this before. I used a combination of the following techniques:

1. I do not attempt to organize the photos on the phone itself. I leave all photos in the "Camera Roll" folder. This is an important step for me as it simplifies all the other steps. (The phone itself will do some virtual arrangement of the photos into location and date sections, that part is automatic, unrelated, and doesn't affect what I'm talking about. I mean, I don't create new folders on the phone and move photos into those folders.)

2. I don't use iTunes or other photo-management software to synch the photos, I had some problems in the past when I tried to do that. Though if you do that, for example if you use one of the apple products to synch your photos, then it should all be automatic when you get your new phone. Anyway, the stuff I do below is only applicable because I don't use apple products to manage my photos.

3. At regular backup intervals (whenever I back up the phone's data in iTunes using the Backup function in iTunes), I also back up the photos from my phone into the following folders on my PC:

- Camera roll
- Videos
- Panoramas

Due to the randomly-named subfolders on the phone making this hard on Windows, I have to do this by opening up a Windows Explorer window to the phone's DCIM folder and performing a search for "*.JPG" or "*.MOV" for example. Then I make another Windows Explorer window to my local backup folder and arrange the two windows side by side on my screen at the same size, both set to display thumbnails of the photos of the same size. Then I can just scroll to the bottom and see the differences. Stuff that isn't in my backup folder, I drag over to it.

3. For putting photos back onto the restored phone: If my iTunes backup didn't restore the photos, then I use Copy Trans Photo to get them back into the Camera Roll folder normally. (Note: I Could have also used Copy Trans Photo for the regular backups up as well, but it's quicker for me to use Windows Explorer for that step).