About 20 years ago I spent about 5 years travelling between the US south Africa and the uk. Very early in that period I met a guy who taught me how to travel. It made a lot of difference.
Always be polite, at check in volunteer your service to help in the case of a rowdy passenger, this got me loads of upgrades. Complain in writing about the little things again loads of upgrades and loads of air miles. Listen to the duty free trolley, if you hear them say they are out of something order that. Complain the you often fly that route, I used to get loads of miniatures for free. Join partner airlines and write to them and say you forgot to claim your air miles when you flew with a partner airline.
I had things going with hotel chains and a big one with Avis, car got broken into in Pasadena no probs but about 40 mins from LAX found a small local place with about 20 cars. We did a real where I would pick up a compact car from L.A. And go straight to the local dealer and swap it for the best car they had. Turns out I was there best customer. Even got a dodge viper once.
Anyway after all this we never had to pay for a holiday for about 12 years. flights hotels and car included.