Project Life has been so much fun this year!
I've tried taking a photo every day, and was really good about it at times and not so good at others. I really didn't stress about it, though. I have a few weeks, mostly over the summer when the boys were away, that I only used one page per week (so, two weeks per spread), but most weeks were a 2-page spread.
I tend to mostly use 4x6 photos with a few 3x4's mixed in when I want a few extra photos for the week. I journal about most of the photos on the 3x4 cards. My intent isn't to document everything that we do, just enough of the highlights and "everyday" kind of photos to give the flavor of our life at the time. When I want to scrap multiple photos, I usually do a 12x12 layout that goes in another album.
I used a big pack of 60 Design A page protectors and have a few left over. I did use a few inserts, like the others were mentioning. For my inserts, I cut down a Design A protector so that it holds fewer photos. There are also other designs that Becky Higgins makes that are smaller - 6x12, 8-1/2x11, and many others. Generally, when I think "insert", I think anything that's smaller than 12x12. I've also used the 6x12 protectors to hold school event programs, and have even just hole-punched brochures and put them in the album directly.
Last year I used the Cherry Edition core kit and journaled directly on the cards. I think for 2013, I'm going to get the Seafoam Edition kit, but print the journaling on from the computer. I've started going back to 2011 and making the cards from my scrappy supplies and I really like the look of the journaling printed on the cards in a typewriter font. We'll see how that goes.
Like Kellie, I like Cathy Z's album. I also liked looking at
Ali Edwards' pages.
Most of all, I'd say to do what you want with the project and have fun with it!