here's a bunch of openers, just look through them and find one that works for you:
collection-of-pua-openers-and-add-yours-vt8124.html
also use the 3 second rule. don't stare at a girl and keep looking at her while you sum up the courage to approach her. you gotta get used to approaching within 3 seconds. because if you take any longer, she'll know what you're up to and snuff you out and probably knock you down a peg or two just by rejecting you.
that's the bitch shield, she might not be a bitch, but she gets approached all the time and uses it to save her the time and effort of letting afc's down softly because they're not worth her time.
so, just approach a girl (when it's just for practice it doesn't necessarily have to be the love of your life, any hb will do) and just open the set (whether it's multiple or not) and engage all her friends and send the target hb a few negs here and there. try it out, and just have fun, it's not a matter of life or death, so just be relaxed and keep a cool demeanor.
p.s. age doesn't matter.