I'd try and remove it immediately. The longer it sits on the paint, the more damage it can potentially do to the finish, depending on what it is. Some tree saps, oils, etc. can be quite acidic.
I would try and soak the spots in water for a while to soften them and then try some removers. I've had good luck with NON-GRIT mechanic's hand cleaning gels. Not great for your paint though. If you use it to remove the sap, rinse with plenty of soap and water immediately after.
2007 E550 4Matic - 61,000 Km - Iridium Silver, black leather, Sport package, Premium 2 package
2007 GL450 4Matic - 62,000 Km - Obsidian Black Metallic, black leather, all options
1998 E430 - sold
1989 300E - 333,000 Km - sold
1977 280E - sold
1971 250 - retired
"And a frign hat. They gave me a hat at the annual benefits meeting. I said. how does this benefit me. I dont have anything from the company.. So they gave me a hat." - TheDon