OK heres what you do...
1) Go up to her but not to close..
2) imagine her as a family member
3) Treat her like shes something you care about most
4) Forget you ever went to the internet to look for help... Which is kind of sad
5) Forget you were ever shy or nervous and she will be somebody you just like being around.
No No No ..... Here's what you really do listen to your heart I know it's hard but just try maybe you'll learn something because if you listen to your heart you'll know just when it's right for you to stop being nervous around your crush because I've been there and I've done that I learned right from my mistakes just try it might work out you'll never know until you try because everybody's different so different things work so just chill out and try your best you'll be fine.
You can't try NOT to be nervous at all, that's just the effect he/she has on you, sorry :)