A major part of being a writer is observation. Until recently I was an elementary school librarian so I had a plethora of material to use daily! Since I left my job, though, I've found that its not as easy to find ideas.
Ideas are all around us but we have to actually put ourselves out there to find them. Currently I'm sitting in a surgery center waiting for my dad's surgery to be over (don't worry, it's very minor) and I'm eavesdropping. Rude? No, research!
The voiced in your head will always sound like you unless you get out and hear other voices, other conversations. That makes for flat characters that are hard to distinguish from each other. Also, you'll hear other people's stories that may give you plot ideas as well. Be sure to change some of the details and definitely the names! Protect the innocent (or guilty)!
There are several different conversations going on around me. One man is on the phone talking someone though an electrical problem with a lamp. One group is laughing about something that I didn't hear (me? Hopefully not...) but they all have different types of laughs. Even this is writer's gold. I peeked at their faces but tried not to stare and thought of ways to describe their expressions.
Today was an easy day to people watch because I had to sit in the waiting room but some days it's hard to find the time. Often I find myself stuck in my car all day carting kids around. Sometimes we forget that even our own kids can be eavesdropped on. It's especially fun to do when they have friends in the car with them. Not only can you get story ideas but you may actually learn something about your own kids.
Even though you may not find yourself around kids all the time, maybe yours have grown up and moved out, maybe you haven't had any, you can still find story ideas all around you. Get in the habit of truly watching people. Start eavesdropping on conversations and don't forget to take notes! Your next best seller might be someone else's conversation!