Commitment Versus Dedication
You might think I'm talking about dedication when I say the word commitment. But they are two very different ways of describing what it takes to become a successful actor. Commitment refers more to the role you're playing. How much of yourself you're willing to lose in order to embrace the character. Fully committing to a role so that the character you're playing truly comes to life. Dedicating yourself might simply refer to taking the time to memorize your lines, or skipping a date to rehearse with your scene partner. Commitment means giving yourself to the role of acting.
In most cases, actors have to forget who they are in the real world. I know that sounds harsh, but it's extremely important to realize that if you're in the middle of a scene and you're thinking about something you (the actor) have to do, or what line to say next, you're not fully committing to the role. And if you're not "engaged", you're not likely to be "engaging" to your audience.
Be Willing to Look the Fool
I can't tell you the number of actors who refused to act out something the role requires because they (the actor) don't do it in "real life." For example, I had one well known actor tell me that she didn't like knitting, so she simply refused to do it even though it was important for the character she was playing. It was something she the person didn't like to do, so she made the general rule that any of the characters she would play wouldn't like to do it either.
As ridiculous as this might sound, it's more common than you think. But it's those actors that are willing to "look the fool" and do things for the sake of their craft that are more likely to find success.
One side note on this thought is that there are some actors who have reached such a pinnacle that they understand what it is about who they are on screen (or on TV) that they refuse to do something because they know the audience who loves them won't expect it. If you go to see a Harrison Ford action movie, you expect him to behave in a certain manner -- and he's aware of this. Thus, he may refuse to act in a certain way, or do a particular activity because he knows what his audience expects out of him. He wants to give them their money's worth and keep them coming to see Harrison Ford movies.
But for those of you starting out, do what's required of the character to make it the most engaging role possible. Fully commit to the role you're playing. Fully commit to the craft of acting and you might just find your star rising faster than you ever expected.