In my opinion your reactions should be genuine, it's your Masters job to find a way to make you react as he wishes. I personally need to feel the real thing, genuine fear, threat, pain, humiliation and my own reactions but that's not the only way to go. Some people enjoy making it a bit more loud or dramatic than it actually would be so if you think you'd like it just give it a try. There's also people who are very much into playing "the perfect sub" which can also be fun.

I'm very difficult as a sub (as well as a person) and haven't been "a good sub" to anyone, but I still feel it's best to be yourself. No matter how things go. The moment you start to fake things or think what would be "the best reaction" or make yourself do things you should do "just because you are kinky and a sub" things start to go wrong.

Enjoy, play safe and be open-minded, explore, define your limits and let your Master learn to play the fine instrument you are. Be honest to yourself and to your parter.

Just my two cents.