Smart Choice for Cursor Processing

It's nice article desribing when to use
CURSOR FOR Loops
Avoid using it
SELECT INTO
Use when query can return atmost one row. Also put SELECT statements in seperate PROCEDURES/FUNCTION. Which can be optimized/cached in Oracle 11g.
CURSOR BULK COLLECT VARRAY [Fixed number of rows or less]
Use when SELECT query will return multiple rows but you know upper limit. If upper limit is very high say 10000, you may want to go for next approach. As it will consume lots of memory.
CURSOR BULK COLLECT NESTED ARRAY with LIMITS
Use when SELECT query will fetch multiple rows and you don't know the upper limit or you know the upper limit but it is very high.

More Detail with examples at:
http://www.oracle.com/technology/oramag/oracle/08-nov/o68plsql.html