Believe in yourself.
Confidence draws people in and if you're exuding optimism and strength, you'll be remembered for those attributes and not for a young appearance. Carry business cards, meet as many new people as you can and hold your head up high.  

Cut out the four letter words.
Soni Dimond, a national public speaker, communications coach and author of Life's a Pitch!™, often reminds clients that it's not just your outward facade that matters - it's the whole package, including the way you speak. "Avoid these four letter words: 'just' and 'only'," she recommends. "These little words can poison your presentation."

Take the valley out of the girl.
Additionally, the word "like" (which is associated with ditzy teenagers cruising the mall) must be stricken from the vocabulary of anyone who is serious about building her career. It's fine to pepper a casual conversation with the "L" word, but in a business setting, it tends to make anyone sound less intelligent than she actually is.