Best Defensive City Placement?

Here's the best placement
1. Build City on a Hill and directly next to the intersection of the river
2. Clear away all the forests and jungles within 1 tile's radius

Delays enemies' attempt to take your cities.

What if they come at you from the opposite side, i.e., the side that doesn't have a river between them and your city?

What if they come at you from the opposite side, i.e., the side that doesn't have a river between them and your city?

A detour will cause a 1 or 2 turn delay.

That's true. But in a thread discussing city placement, the fact that you might have time to build an extra unit really means absolutely nothing in terms of the actual tile your city occupies.
Also, what if you place that city before you know what direction the aggressors are coming from, and they come from the non-river side? Or, what if you end up in a war with enemies who come from both directions? One civ may be delayed by the river, but the other might not.

I'm not disagreeing with you at all: the benefits of building by a river are numerous, and defense/attack penalty of water-crossing is helpful.
I'm just saying that telling people that the best possible defense for a city is by placing it beside a river must be further thought through.

If you really want to see a city with good defense, check here:
http://forums.civfanatics.com/showpost.php?p=3361894&postcount=166
and also look here:
http://forums.civfanatics.com/showpost.php?p=3373472&postcount=207

Those cities won't be attacked any time soon.

If you're building on hills, try to pick a plains hill. They give 2 hammers in the city tile.

That sounds about right to me. I would add that you should also try to make it a hill with no adjacent hills, so that the enemy can't occupy the adjacent hill square and screw with you.

Also, if you can get a place with hills/forests on your city's outer boarder they provide additional buffer of protection by slowing an enemy advance.