First, print the thing out, all 114 pages (pdf), and hand it to your Senators. Best if you can say "I've read it, I expect you to take the time to do so yourself." For extra credit, take a highlighter to the printout and mark up the sections you consider problematic.
Bring an accomplice with a vidcam. An admission that they haven't and won't read the bill makes nice youtube, come re-election time.
Statement of U.S. Senator Russ Feingold On Preventing the FISA Amendments Act from Being Jammed Through the Senate "I'm pleased we were able to delay a vote on FISA until after the July 4th holiday instead of having it jammed through. I hope that over the July 4th holiday, Senators will take a closer look at this deeply flawed legislation and understand how it threatens the civil liberties of the American people. It is possible to defend this country from terrorists while also protecting the rights and freedoms that define our nation."
How to find your Senators' appearances? Start with their Senate and Campaign websites. Next, search Google News for "YourSenator'sname Parade" "YourSenator's name Barbeque" "YourSenator'sname Picnic" "YourSenator'sname fundraiser" If you don't get hits, make a Google Alert. Post any scheduled events you find below in comments.
Senator Feingold plans to introduce 6 Amendments. He explains them, not in great detail, in Fact Sheet: Potential Feingold Amendments to FISA Bill.
Print it out too, and when you catch your Senator, ask that they support them all.
Dodd-Feingold Amendment Stripping Retroactive Immunity
Feingold-Webb-Tester Amendment to Provide Protections for Americans
Use Limits Amendment
Prohibiting "Reverse Targeting"
Prohibiting "Bulk Collection"
Congress Access to FISA Court Materials
If your Senator won't budge on immunity shift the conversation to the problems with the parts that go forward. If any Amendments pass, and the Senate approves the revised version, it throws the whole deal back to re-negotiation with the House, which would then have to start it's process all over again. The package can not go to Bush's desk until both the House and Senate pass identical versions.