Which is why you should only give warranted compliments.

You're right, telling someone bald that they have a great head of hair is not going to work well.

Fortunately, virtually everyone has something you can compliment them about. Even if they're a surly old frumpy shopkeeper, maybe they keep their store super clean and organized. Maybe you're impressed by their loyalty to serving the community for so many decades.

Never say anything that isn't genuine. Fortunately, most people have qualities you can be genuine about.

My approach to self-transformation these days is to take on long term projects (months, years) aimed at changing habits from the outside in and inside out simultaneously.

If I was interested in praising people I would task myself to look at people when I am out in the field and find some kind of praise I could give them. Maybe I give them this praise maybe I don't. Doing this over time I will find it bubbles out of me, the desire to give praise and the words to say comes more and more frequently and quickly and it will come out increasingly. Whether the feeling comes spontaneously or whether you consciously plant a seed and let it grow, it comes across better than if it forced.

Lately I've been practicing deep and rapid synchronization when situations are favorable and I'd say I favor listening and observation over praise except in cases where my feeling is very strong, such as somebody really helped me. There is a long list of language patterns that somebody might read as "somebody is trying to butter me up" and in this mode I avoid them almost entirely. It is important to stay in a "I'm OK, you're OK" [1] frame no matter what happens and to have control of your microexpressions (one wince can set you back permanently) which comes not from an act of suppression but rather going into a situation feeling full and practicing radical acceptance.

[1] see https://en.wikipedia.org/wiki/Eric_Berne

I guess I should edit it to just compliments are my biggest red flag, and it's born out of experience. These people are looking for something either now or in the future, and this bullshit false niceness is simply their way of cultivating a network of people that they can use.