altering the neckline on your t-shirt

[Tiggeroo]

While I was on vacation i bought some cool t-shirts that I want to wear. But I just, well I think girls with less busty figures look better in crew neck t-shirts. I always feel uncomfortable in them. I want to cut the neck line some so they have more of a v-neck. I see girls do it, but whenever I try I mess up. Any tips.