Do you read every day?
You should be. Find something. Non-fiction. Something without a lot of emotion. Something that you're not going to ry to "act" by accident.
History books are great for this. The History of Acting, something like that.
Read four(4) pages, or about 5-10 minutes every day. Out loud. Don't stop for corrections, just make yourself keep talking. This does 2 things.
1 - it gets you used to reading off the page, so if someone hands you something, you're not stuttering through it
2 - it gets you used to hearing yourself. Half the time you're auditioning/acting, you too damn busy thinking, "Did that sound right?" When, really, it's got little to do with the actual words, and more to do with the feeling that delivers them. The words are just information. The real scene is in the emotion.
Oh, and DON'T read something all emotional. Get a history book, or someone's autobiography, or The History of Acting. It should be something that you're not trying to "put emotion into."
Read out loud every day. You'll be a better actor because of it.