As an Alaskan fishing guide dealing with several hundred clients per season, I get to see more tipping behavior than most. I agree that 10% is a very fair amount, but lest you think the guides are getting rich, consider the fact that many people leave no tip at all, and in comparing notes with other guides, I estimate the average to run closer to 5%. Nothing takes the wind out of your sails like being handed a $10 bill or a handshake after catering hand over foot to a guy for 6 hours on a $400 trip, getting him a fish limit, cooking him a shore lunch, watching him mangle your personal equipment and lose $20 worth of your tackle, and being told it was the best trip ever. Our overseas friends are noted for this, and many in this country also plead tip ignorance. If you're happy with your trip, tip accordingly, and consider how much work your guide did for you as compared to what the waitress (no offense to watresses) does for her 15-20%.