Avoid icing, and clouds in general. Icing costs a lot of speed and fuel, clouds also slow you down. (just slightly, but every bit adds up)
I made the mistake of looking at distance remaining in little navmap which doesn’t account for the 6 gallons of fuel you can’t use. Hence I fell short on my first attempt to Alert. I could have easily made it by using a leaner mixture and fly slower. On my second attempt I got stuck with icing and used the ground effect to save fuel, flying low over the water.
The longest distance I made with the Bonanza was to Easter Island
I wrote down all the settings I used, speed, wind, air temperature and mileage. It’s a fun puzzle to extend the range, albeit a long slow one 
12 hour flight from San Felix to Easter Island!
Watch the air temperature and avoid clouds.