Select or make your dress!
Pick a plain dress so the pattern won't clash with your embellishments.

Next, I recommend laying out your buttons where you want them to be and taking a picture so you can look back and remember what goes where.

After doing that simply thread your needle and begin sewing on your buttons.
I recommend going through 3 times if using all purpose thread and tying a doulbe knot after each button.

Once all of your buttons are in place, you can add an assortment of very small to large saftey pins on the other strap.
I used this patter:
3 really tiny ones
1 small one
3 really tiny ones
1 medium/ standard one
3 really tiny ones
1 large one

After that you are finished!