Here, courtesy of our friends at NASA, is a topographical map of Mars. What you will notice is that the north of Mars is flat lowland plains and the south is crater-pitted highlands. This is important to know if we're going to terraform it.
It's pretty easy to terraform Mars. (This is obviously false but let's play along). All you have to do is pump greenhouse gases into the atmosphere. This will warm the planet, causing the carbon dioxide locked in Mars' dry-ice poles to sublimate back into the atmosphere, thus magnifying the greenhouse effect. It will also raise Martian air pressure above the Armstrong limit, the point at which air pressure is high enough that water no longer boils at human body temperature. Then import some water and oxygen, both of which substances Earth has an overabundance of, and Bob's your uncle. The only concern is that Mars has no magnetosphere, meaning the atmosphere will be constantly eroded away by solar wind, but you can get around that by bringing shipments of extra gas in from Earth or Venus on a regular basis.
(I am not a scientist! I am not even the guy from XKCD. I just read some Wikipedia articles. Although I'm pretty sure that's all the guy from XKCD does.)
What's important here is water and air pressure. All the water is going to drain into the lowlands. That's what happened back in the days when the Martian surface had rivers and oceans. And the highlands might not even have breathable air, especially the red bulge on the right, which is the volcanic plateau of Tharsis. The best Earth comparison to the surface of an only mostly terraformed Mars is likely to be the summit of Everest.
|as we know, mars is indistinguishable from utah|