Ho searching a string in a LONG or CLOB?

I'm porting a database from SQLServer to Oracle 8. I have problem with memo SQLServer Type. It can store text and it's able to perform search inside it.
I tried to do the same thing in ORACLE, but I didn't succeed. (Varchar2(2000) is too short for me. I'd like to use CLOB type or long).
Who can help me?

                                                    Andrea Collamati