All you need is scissors and a t-shirt!
When choosing a shirt you can either use a size or two larger, which I did, for a baggy tank top or you can use a t-shirt that is your size for a more fitted look.
(I found these from Michael's for less than $5)
When making all of these tanks, I started by cutting off the sleeves and the neckline. I decided to plunge low for the sleeves, but you can cut as little or as much as you like.
Same thing goes for the neckline!
For the "cord" style (my bright blue and white shirts), I pulled in the straps and used a scrap piece of t-shirt to wrap them together.
Begin by tying the scrap t-shirt in a knot towards the top, wrapping it around a few times, and end it by knotting the end of the scrap piece to the shirt and tucking the ends.
You can make the cord long or short.
For the "tie" style (my pink shirt) I simply pulled the straps in and tied them together with a knot, allowing the end of the ties to hang down.
And for the "weaved" style (my dark blue shirt) I used this tutorial:
"T-Shirt Weaving" and I did it to the back of my shirt!