Baby steps to improving my self-esteem?

Hello,
So recently I am re-making myself. I'm exercising (I'm not overweight, I just want to tone and be healthy), I'm eating right. Along with that, I'm somewhat pretty, and I keep up my outer confidence well. I feel good about my looks, my style, etc. I'm whitening my teeth, and using tanning lotion the odd time (I'm very pale, but now I have a healthy glow) and I'm washing my face as I should. Normally I tend to procrastinate about the basic skin care, diet, etc so that's an improvement.

Along with those, I got a close friend to help me with my inner confidence. When I'm alone I'm confident, I feel good about myself (I would say my confidence is like 7 out of 10), and when I'm with her it's about 6. But, whenever I'm in a situation that I'm not used to, or I feel out of place my confidence goes down to like 3. Normally this always happens when I'm with a group of people that I'm new to, and I don't know very well. I become very very quiet, and my convesation skills go out the window. I've had some bad times in junior high, so that's probably a reason of why I don't feel comfortable (I'm 16 now).
So I've got a supportive friend who will help me gain self-esteem. We've started yesterday by making lists of my goals, acheivements, strengths and weaknesses. That actually helped. But we don't really know how to continue in a way that will slowly edge out my comfort zone.
Eventually we will take my new skills into a small group of people, and practise being more open. But I'm not ready for that yet, so how do we get there? What can the two of us do for practise? Just small things that will help me become more confortable as me.

Any tips of improving confidence will help, and past experiences too. Thank you :)