Charisma has a lot to do with personal charm. Imposing your personality on someone should be subtle and not overdone; else it may repulse the person. Here are a few tips to be charming in an innocent way:
Try not to be loud in any situation. Be calm and pleasant while relating to others and they will perceive you to be charming.
Let your reactions be consistent. You are unique, let not how others react affect the way you react to situations. This develops a genuine aura about yourself and makes people notice your personality.
Your eye expressions
Your eyes give away your emotions more than you think it does. The way you feel can be easily understood by your eye expression. Avoid the ‘mean-eye' expression. If you keep a happy-go-lucky positive attitude about yourself, let your eyes show that as well. Be sure to smile more often and your eyes will reflect the right emotion.
Be subtle in your body language
Let your actions be sober. Do not be too loud with your body language or your voice tones.
The most important thing to do is smile. Smiling uses lesser facial muscles than a frown and it is plain easy to smile often. Let others feel a happy aura about you at all times.
Think before you speak
Usually, people do not think before they speak and end up saying something they don't intend to. Make sure your words are clear and there is no double meaning to what you say.
Use your sense of humour but not at the expense of others
A sense of humour is certainly charming, but not at the expense of others. Make sure you do not hurt others when you attempt a wisecrack. Let your sense of humour be subtle and gentle.
If you can stick to these basics, you can be sure to assert a charming and innocent personality which is loved by many.