A couple of other tips:
1. When you apply it, apply it just to the bottom lip at the center (and a little bit towards the sides) and touch your lips together. When you do that, it's harder for it to migrate in large amounts to the areas where your lips meet.
If you need to blend it or disperse it a bit more, lightly roll your lips together in an inward direction. By roll, I don't mean rub them together. That should spread the product around, but not smear it or allow too much to accumulate in the corners and where your lips meet.
2. Another key is to be mindful of how much you apply. A lot of people tend to slather lipglass on when just a bit will do. I will admit that I am occaisionally in that category, btw.
I fix it by putting my index finger between my lips (towards the back of my lips) then press my lips down on my index finger. It removes excesses where your lips meet and at the corners.
3. (Gently) Exfoliate your lips on a regular basis. With either A) a washcloth (wet with warm water), B) a baby toothbrush and some vaseline or C) a treatment like MAC's or Tarte's, then condition.
And lastly, as others have said, if it works for you, condition your lips before application. Prep + Prime lip may also help you keep your gloss in place.
HTH