Normally my embark site looks like this:
1) Surroundings: Normally I go with untamed wilds, but sometimes I might shake it up a little and go into a evil/good biome.
2) Trees: Woodland or more
3) Vegetation: Not important, but more vegetation breaks ties
4) Temperature: Anything but scorching, but this usually falls in the warmer half of the spectrum because of the previous two preferences
5) Minerals: deep metals, shallow metals, flux stone if possible
6) Some soil is ideal but I could go with anything
7) Clay if possible
8) No aquifer
9) Some form of fresh water is preferable, if not I can just get it from the caves, so it's not a big deal
10) Neighbors: No tower.
These are all soft requirements and it might change depending on how many potential sites I can find.
However, with the addition of boats, I'll likely drop most of those requirements in the pursuit of constructing the greatest Dwarven Seaport ever built.
While I'm listing my embark preferences, these are required for me to consider it:
1) Minerals: shallow metal(s)
2) Trees: sparse, but only if there's stone coal on the map. If not, at least forested.
3) Temperature: Not scorching
4) Neighbors: No tower
I've played this game since 2012 (although I've only really understood it since 2014) but I consider myself far from good. I've yet to try thing like reanimating biomes, embarking next to a tower, terrifying biomes, or desert or glacier embarks... I tend to stick to the safe side and build a bustling city. I think that because of this, I'm missing out on a lot of fun. Perhaps I'll embark near a tower in my next fort before the next release.