A few options would be:
- Always pick the highest-voted answer. This relies on the asker either keeping this up to date as new answers get voted up, or just picking the highest voted after N days from the asking.
- Never accept an answer and just rely on upvotes for rep.
- Pick whatever answer the asker likes most based on whatever criteria he/she feels like (humor/accuracy/whatever-they-agree-with).
- [Edit add:] Always accept Fishtoaster's answers because they are, by definition, the best.