I don't do anything special to organize. My photos go into Lightroom in folders by day. For each week I want to scrapbook, I select the photos and create a Quick Collection with them.
I use whatever photos I have -- I don't try to take a daily photo. Sometimes my 2-page spreads have a ton of photos, sometimes only a couple. If I don't have very many, I try to include other things like screenshots and lists (like Favourite TV Shows or something else random).
I find journaling by checking out my Facebook posts, texts, google calendar, instagram feed, and emails. Sometimes I google the news for the week to see if something big happened that I want to note, or the weather.