What she said!

A good layout first.

Chose the things with the least selection first, then your choices are always expanding instead of narrowing.

Assuming you have the overall "look and feel" decided, do what Joseph Corlett said ... whatever has the smallest selection.

Unless of course you have totally fallen in love with ___whatever__, and everything is picked with that item in mind.

Agree with what has already been said. There were only two things I knew (the only things, at first) was that I wanted white cabinetry and granite counters. So white cabinets, then chose counters. One of the stones at the stoneyard "spoke to me". It was love at first sight. This often happens. You just know. All my other choices went from those 2 starting points.

Backsplash was the absolute last thing to choose. After everything else. In fact, my kitchen was fully installed and done except for the backsplash. I wanted to live with the kitchen for a while, see it different times of day in different lights. I am glad I waited to choose the backsplash.