The most hassle you get is on the beach path around the Bonsai Cafe where the beach sellers hang out, waiting to pounce on unwary, and very white tourists. Sometimes they'll walk with you along the beach path for some distance, chatting to you, with a script that includes asking you where you're from, where are you going, do you want a massage, you come look in their shop, you remember their name (usually Wayan, not difficult to forget), you look in their shop later.
I find that having a suntan and wearing Bintang t-shirts deters them to some extent, but the hassle isn't too bad. Just be polite, smile, talk to them if you want, say no if you don't want their services, tell them you have too many sarongs (clearly a lie, as it appears that no woman can have too many sarongs). Don't ignore them, or shout at them, they're just people trying to make a living, and getting angry just makes you lose face.