index strategies

Can someone point me in the direction of some good, useful info
re: datamine index strategies?

I have one BIG table (apr :
Attribute | Type | Modifier
-----------+--------------------------+----------
dnis | text |
cli | text |
iplogin | text |
brand | text |
begintime | timestamp with time zone |
endtime | timestamp with time zone |
ipaddr | text

Any one of the columns may be used in the where clause of a
select statement.
There are also aggregates used in select statements
(e.g., sum(endtime-begintime) group by iplogin AND count(*)
group by iplogin).

I have a small clue (ha!) about indexing but want to know the
proper way to attack the indexing strategy.

Any info given is v much appreciated.

Val