the way you could do this is as follows,

exp username/passwd@instance_name TABLES=(schema.t1,schema.t2,...) FILE=your_file.dmp DIRECT = Y
COMPRESS = no

If you have setted the ORACLE_SID= ... , then you don't need to specify the instance name. If you are doing this from a remote system then, instead of instance name you would have to use the service name (db1.xyz.com) as you have specified under the tnsname.ora file.

Now comming to the point of import,

imp username/passwd@instance_name TABLES=(schema.t1,schema.t2,...) FILE=your_file.dmp ROWS=Y

to do it between different users then you would have to use the FROMUSER and TOUSER clauses


I hope this would help. If you have any questions, let us know.
Sam