I'd start by just polishing the pins and pin bore in the trigger and take one coil of the trigger return spring, then check it after putting it back together. You might also try powdered graphite, it's been reported to reduce trigger weight without any work. Be careful using the method Aaron mentioned, several members have broken the sear notch off the hammer doing that, as he said don't put too much pressure on the hammer. Mic McPherson mentions 20lbs in his book, I asked him if he ever broke an hammer, said he hadn't, but he had only worked on older H&Rs, newer parts may be more brittle.
Tim