You do not mention your baby's age, but here's the rule of thumb: It is not possible to spoil a baby who is six months or younger by responding too quickly or too often. In those early months, you want your baby to learn that the world is a safe place where his/her needs will be met. That means responding without unnecessary delay, although sometimes all you need to do is go to a crying baby and smile and coo at her to see if that simple an interaction can settle her.
As babies grow to be toddlers, it is not necessary to respond instantly all the time because that is what tends to teach them to expect instant gratification. As a tuned-in parent, you can begin to sense when it's appropriate to respond quickly and when you can stretch him a bit. If a 14-month-old is in the high chair asking for "mo," you can respond by saying, "You want more! Good for you. Mama can get you more. First, I have to feed the dog. See, here's the dog's food. Now I can get you more. Thank you for asking so nicely." That may seem like a lot of language, and it is, but by engaging him and pausing, he's watching you feed the dog, and that helps him to modulate himself and learn a little patience.
There's no magic formula to this but you're right to recognize that our behaviors and attention are what "spoil" a child. But if your baby is still a baby, you just may be over-thinking this.
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