Before everyone starts screaming at you to go to a boot fitter, which is still the right move, look at your feet.
Wide or narrow?
Flat or high arch?
Where's the widest point?
Also, think about your preferences regarding footwear... Sounds weird, but it works pretty good in a really noob way (the whole post is aimed at being a noob's guide to picking a boot by yourself). For instance, I am slightly flat-footed but despise any kind of very supportive sneaks. Ergo, Nike's with their high arch are out of the question. I also have a somewhat narrow foot throughout, yet the largest point of my foot is pretty near the toe and more in the mid-wide range. Ergo, I need a roomie toe box. If we resume, regarding my feet, narrow, but wide toe box and minimalistic -> INNOV8.
In boots, that's a FT. Nike would resemble more of a Salomon with its higher arc and wider fit.
Those are the ends of the spectrum...
Then there are the calves!
But got to a boot fitter.