What I've found works realistically is not to always misinterpret things but to simply fail to put things together. When the rest of the party comes up with a four part plan, the stupid character won't see how the parts fit together to accomplish anything.
This method is less amusing than always being wrong, but it lets you play a dumb character who isn't comic relief. If you're the bumbling idiot who always gets things exactly and precisely wrong, the party ends up laughing at and ignoring you.
The other factor of this technique is figuring out how your character reacts to being dumb. I've played three successful stupid characters and they all took their stupidity in different ways.
My half orc got angry about it. When he didn't understand something he'd frustrate quickly. But when he did get something (or think he did) he'd get extremely smug and nobody wanted to tell him he was wrong.
My stoner didn't even know he was dumb. He had a different enough niche than the rest of the party that he could plan out his own shenanigans without getting in anyone's way.
My half ogre was blissfully ignorant. He did whatever he wanted when he wanted. The silly talky folk had to come up with plans to accomplish everything, but Tibor just did things. In his mind this made him superior to the rest of the party.