Oracle Index Question

Hi 

I am new to Oracle. We have a Oracle 8i running on Solaris 8 (Sparc)
Any way I have a question re indexes... 

we have this scenario
table1.col1, table1.col2 and table2.col1 

the common field  between the two tables is col1... 

When running queries I cannot use inner or outer joins or use oracle
hints because I have no control over the application that generates
the query.

Is there any kind of index I can apply to table1.col1, table1.col2 and
table2.col1 that will spead up my queries. 

Some thing like a foregin key index etc.. but I donot know.
If any one can make any suggestion ? 

Thanks