First of all, buy a Barbie that looks somewhat like yourself. I got mine on eBay and I picked the first one I found with dark hair - it's rather tricky finding a doll that isn't blonde.
Next up, pick a photo of yourself to work from.
First of all, I gave my doll a hair cut. I wear my hair at a side parting, so to give the doll the same, I cut off a small amount of her hair, glued it in the center of her head, folded it down to the side and then added a little bit of glue just above her ear, to hold the hair in place.
I also cut her hair shorter and layered it a little - Barbie's have seriously long hair.
To get the correct colour, either use permanent marker pen or semi-permanent hair dye. If you're going to be dying your own hair, you can use a little bit of this to do your dolls hair too.
To make your doll clothes, draw around her body on to paper and make your patterns like you would for real clothes. A great way to make clothes would be to trace around existing Barbie clothes and use these as a template to make your own ones.
Pin your patterns to the fabric but leave a hefty margin around the edge - you can then sew the clothes straight on to the doll to get the perfect fit.
I made my doll my favorite kitty ear hoodie and star skirt - because I make a lot of my own clothes, I have lots of remnants to make Barbie some matching clothes.
I also made her a miniature version of my Blinging Name Choker, using the same instructions but on a much smaller scale.
I added little bindi crystals to the corner of her eyes because I love wearing bindis.