#1
as there are many different ways to construt chords how do you know which pattern is the most suitable for different songs
cheers
~Kainique
#2
i do it on how easy it would be to get to the next chord.
i always think that my fingering is a little strange (or should i say different) to the other guitarists in my band, even on leads, but whatever works for you.
--------------------i'm definitely the alphaest male here--------------------
#3
Trial and error. Use your ear.

The following are all D-A chord changes:

-2-0------2--5------2--9-------2--12--
-3-2------3--5------3--10------3--14--
-2-2------2--6------2--9-------2--14----
-0-2------0--7------0--11------0--14---
-x-0------x--7------x--12------x--12------
-x-x------x--5------x--x-------x--x----


Which one do you like best? None of them are better than the other, its all up to you.