Age: 3 months
I don't wish to wait for her to cry whenever she needs food.
What are the signs other than crying which indicate that the infant is hungry?
At 3 months they don't actually have many ways to communicate. Crying isn't an emotional problem for babies - they cry to communicate pretty much any form of discomfort.
You may see your baby try to nuzzle for milk if you are holding her, or she may curl up or arch her back if she has a hungry stomach, but the simplest route is to learn the different types of crying noise she makes and respond when she cries.
Crying's a clear sign, but also be on the lookout for your baby...:
Also, I want to point out that at 3 mo your infant doesn't have that many abilities in terms of communication... They don't move much, they don't nuance cries, they don't talk. They basically feel lots of things but have a very limited range of (also limited) tools to express them.
Don't worry about the crying: it's just the same as you calling the waiter at the restaurant and saying "please".
Just make sure to react accordingly, and they'll calm down quickly. If they don't, it probably wasn't the right reaction. (Though it's not even guaranteed as they don't always know themselves what they expect - which is another issue, but that happens - or can understandably remain upset for a little while)
Infants cry, it's their job. Some babies are really good at it. At 3 mos old, it's almost the only thing they know. They cant even hold their head up or make their hands do what they want them to do.
"Your kid will cry. Don't feel bad when they cry. Just help them deal with whatever they're crying about."
Blockquote for emphasis because it is aaaalllways applicable... 3 mos, 3yrs, 33 yrs.