Wrapping handlebars with bar-end shifters...

[nuliajuk]

I've always done it bottom to top (from the shift lever up). I don't notch the tape because it's easy for it to tear at the notching point. Instead, the tape is wound under cable housings about half-way up the handlebar.

[Sky King]

depending on the look you want, you can also leave the cable and housing on the outside. Then if you need to replace you don't have to take the bar tape off. I will confess I am not the skilled wrapper but the DH is. He goes from bottom to top.