try cutting the lashes to fit the length of your own lash line.
use little nail scissors to cut a few off the inner corner of the strip.
and always use waterproof duo glue for performances. i learned the hard way. it looked like a spider was crawling down my cheek!
my friend does eyelash extensions. if you have any questions about them you can read about them on her site
http://eyelashextensions.ws/
it has lots of good information.
good luck. and make sure who ever does you extensions uses only sterile or disposable instruments, for your protection.