^Well, that's what the tattoo artist is for!
I consider myself an artist -- at least, my drawings are pretty good and my paintings are alright, so I drew some of my designs, but the tattoo artists' input was invaluable, because they know what works in their medium. I worked with them and changed things around to make turn my art into good tats. Find a great artist, explain what's in your head, and let them worry about transforming your thoughts into pictures!
I think for my next tat I'm going to do just that. My best friend and I finally agreed on something we both want for a best friends' tattoo. We both like the idea of cats, and so we thought something that would be a tribute to my cat Max and her Snowball, both of whom we had when we met each other as teens, and both of whom died within the past three years. We want to aim for modern traditional style, but the tat has to complement both our existing work. We want the cats to be recognizable for who they are, but also somewhat stylized. They will complement eachother well, Max was a medium hair tuxedo, and Snowball, well, let's just say she wasn't especially creative when naming him. Anyway, we're going to go to a good artist, give her the details, and let her make the design.
That will be awhile though, because we are both broke.