Indices types, what to use. Btree, Hash, Gin or Gist

Hi,
I have several fields that use to match with my queries. I am curious to
what index types is best for what. Here is some examples that will help you
understand.

Say I have a 1000 000 rows.

Speed is of the essence here, insertions and updates happens relatively less
frequent than search.

I want to match against a boolean field, that is, only true or false is
possible. I am thinking Btree but not sure.. correct?

Match against a field which is an big in and contains the ids for the states
of america (say 50 different values), a btree again?

Against an integer field? Using > < = and between

Date (no timezone), I would like to have this field presorted in desc order.
How does that creation look like?

I understand the Hash is not recommended. When should I use the Gin index ?

Thanks in advance / Moe