Thanks Haywire.
How about if i had to say "yes i think so too"
I guess you could say "Lo credo anche io."
I guess it depends on how formal the situation is, keep in mind I'm no native speaker and I "learned" Italian from friends in my late teens so I can only imagine the mistakes / slang I picked up...
But if we were talking and someone said something like...
"Questo film e' noioso, scappiamo adesso."
I'd just reply (in an informal situation) "sul serio" or someone would say "si si, concordo con lui"
Which, for all intents and purposes, meant "Yeah I think so too."
If I were in a formal setting, like talking to adults with whom I didn't know well I'd just say something like "Si, concordo con Lei."