I got this idea from Orly's diagonal french manicure.
I took a stab at this, and tried out several color combinations before I actually went for the style. It's a really simple process. First, I applied a base coat, let that dry for 10 minutes. Then I applied two coats my base color, allowing 10 minutes after each coat. I actually went out for a few hours, and this allowed my nails to dry fully before tackling the second color with tape. It's extremely important to let that base color to sit for a while, and dry completely. If not, the tape will stick to that base color, and rip it right off.
Once your comfortable with the dry time, line up your strip of scotch tape, at whatever angle you want, with how ever much space you choose. Then, make sure the tape is completely on the nail, with no bubbles in the tape. I had issues with the bottom corner of the tape. It's easier if you line the bottom corner of the tape, with the bottom corner of the nail (I hope that makes sense).
When you're ready, go ahead and apply the top color. Try not to let the color sit too long before applying. If you do, they will bond with the tape, making the rest of the tip peel. It's best to peel off the tape right after you're done applying the tip color. This shouldn't mess up the color.
When your done, let it dry for a bit, and apply a base coat. You should end up with a design similar to this:
I paired OPI's Skull and Glossbones as my base color with OPI's I Vant To Be A-Lone Star as my tip color.
PS, remember when I said I would take a picture of Orly Oui before I took it off? Yeah... that didn't happen. I'll apply it again, and post pictures then. It's so pretty though!!!