It depends on the tree you type you are planting, but you want to plan for what you just dealt with. The future size of the tree is what should be your guide.
Also consider the amount of water the tree needs (if a higher demand, best not to put it near the foundation), the root spread (which is often very different than the canopy size), and the aggressiveness of the root system (some types of poplar roots will work through foundation walls). Think about where your service/sewer lines are, as well.
Of course, you need to look at your local set-back guidelines. Around here, you can put a tree on the city owned portion of your lot, but the city is allowed to remove it if they deem it to be necessary.
Personally, I prefer to use trees native to the area, if possible, as the investment can be significant. Giving the tree the best chance to survive makes sense to me.
I'm against some of the columnar hybrid trees, as they tend not to maintain their "columnar-ness".

Depends on tree, buried utilities, proximity to house, etc.
My rules of thumb:
- Tree roots generally cover an area 2x the canopy area. But it can vary by species. ( http://blog.davey.com/...vasive-root-systems/ )
- Don't plant over septic tank or drain field.
- Don't plant over gas service or sewer connection.
- Don't generally plant within 12 feet of house to avoid damage to roof, eaves / gutters, foundation.
- Think about the cleaning the leaves from the gutter. Do you want that?

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Remember - It's important to be comfortable in your own skin... because it turns out society frowns on wearing other people's

I recommend planting it where there is dirt.