Dribbble is an invite only social network of talented designers who share snapshots of their work. There are no hacks, you can't buy your way in, and there are no hidden shortcuts. Most of the designers earned their place on Dribbble and are very talented. You have to excel at design and have a solid online portfolio if you want to stand out among the hundreds of other people looking for an invite.
I learned the following on my quest for a Dribbble invite:
The possibility of failure makes us feel vulnerable but as a designer you need to learn to take risks in your work. If you concern yourself too much with what others may think you might develop a designers block instead of creating new designs.
Don't take things personally
Without trying you can't grow or gain success. It's essential to accept criticism and if you do get poor feedback over a design you have to remember to move on and not dwell on the past.
Always be designing. Demonstrate your passion, drive, and willingness to learn by being a prolific designer. Learn to work faster and work on multiple designs at once even under imperfect conditions.
You can read my blog post about getting drafted on Dribbble here.