I traveled from KS all the way to northern Cali, down the ENTIRE coast line and back in a month gas jugging ~5,000 miles. This is what I found worked best. Confidence and looking presentable. Have a map on hand and say something like 'Hello! My name is ____________ and I'm heading to (find a town 50ish miles away) for an interview. I didn't account for food during my travels and I ran out of gas. Could you help me out with 2 gallons? I hope that will be enough!' 2/5 people will help. Others will either ignore you or say no. Sometimes, about 3 times a day of full time gas jugging, youll get cash kick downs which are awesome. And in an ever rare situation, youll get those people that are like "push your car over here, Ill top it off!" This happened to use twice in a month of traveling, mainly in the midwest.
Also, only stop at travel stations onthe highway. Stations like Loves and Flying J's etc. Theyre easily identified by the Christmas colors seen from the highway. Red and green. Everytime we would see them, we would all yell CHRISTMAS!!!! and then go jug for an hour or so (we were filling an astro van)
Be sure to say god bless and thank you, even if you aren't religious. Because to them, it means a lot. NOW to combat the scamming people thing that Im sure will ensue this topic. They feel genuinely good about helping you. You get gas and they get the feeling of a good deed helping someone out with $7.00 of gas.