The most important thing is to remember that they are just people, doing their job. So take a breath and realize that there is no point in getting all crazy because they are just like you. Put yourself in their position. While it is flattering for them to have adoring fans, and while they will usually treat approaches from fans kindly, it is not really nice for them to be bothered all the time while trying to eat or while they are just going about their business.
The second thing to remember is that you are NOT a fan, but an industry professional. If you act like a professional, you will be treated like one.
Lets take this for example, just an hour ago our team was having lunch at albergo quattro fontane, just outside the festival. After sitting down we realized that Viggo Mortensen was having a lunch meeting just across from us. And then we noticed several other stars, and that they were actually preparing to have interviews at the restaurant. We remained normal, didn't gawk or bombard him, and just enjoyed our lunch. At desert time when the waiter/manager was convincing us to have tiramisu, Mortensen engaged with us and the waiter and we all had a small laugh following some witty comment from him. He got involved because he saw that we were cool, calm and collected. While we didn't walk away with a photograph, we walked away with self dignity and the fact that Viggo Mortensen engaged in a conversation with us just like regular people do, which is invaluable to a fan of his work.
So since we have been here, here is where we have seen some stars. As fore mentioned we saw Viggo at albergo quattro fontane, and we saw Laurence Fishburne at the Hotel Cipriani (on Giuidecca) who was also enjoying a coffee just a few feet away. Hotel Cipriani is an elegant hotel, and the favorite of many stars who visit venice. The Hotel Bauer includes a luxurious ultra elite spa, another hot spot for stars.
So now we move on to press conferences. The press conferences at the Venice Film Festival are ridiculous. People rush in to get the front row seats, they mob and run to the stars at the end, and you end up breaking a few ribs but getting out with a signature. So here are the BEST ways not to suffer a fatality and to get away with a nice piece of memorabilia and your self respect still intact. 1) If you have a videographer, or anyone with "radio/tv photo" accreditation, you can get into the conference room before it actually opens to set up your camera. Personally I just say I'm setting it up and then leave a couple of bags on the seats that I want while I pretend to set something up at the back. This has worked every time, and I have sat front row and center. This only works if you have some visible camera equipment and the "radio/tv photo" accreditation badge. 2) Provided your excellent seat, you are now just feet away from the stars, directors ect. which means you will have no problem getting up there for a signature. Have your pen on hand, and when you see people in your peripherals charging, walk up to the front like you own the place because you will get there first and have time to give your star of choice a coy smile and get an autograph. 3) Photos. If you want to get photos/videos, bring a small digital camera and a scarf. They don't allow you to, but you can get a couple shots in when they first enter if you keep it ready on your lap.
Well there it is. USE IT WISELY. Remember, respect yourself, the stars, and your fellow industry delegates and maintain your sense of cool and calm. They are just people, and if you appreciate them you won't harass them. Hope this helps you have a great festival!