Try speaking into a tape recorder. Tell what you believe is an exciting story and play it back. Listen carefully to how you sound.
You might be surprised and sound more interesting than you believe you do or at the least you can use it to work on your "delivery".
I am southern and always believed I had a slow, thick, typical southern accent.
I listened to a recording and I could not tell it was me. I speak very quickly and have almost no accent.
Caffeine, a good workout, or talking about something that is actually exciting to you :) One of, or a combination of those three should get the blood flowing. After all, it's hard to be excited if you're tired, bored, or trying to fake it!
You cannot change physically the way you talk, but you can change the tone, if your usually quite mellow, higher your vocal chords ! and be more loud and exciting when you talk, or suck helium? :)
Like I don't sound boring when I talk and stuff...to show feeling in it...you know?
Cos my voice is a bit boring...