You should endeavor to understand different meows of a cat. A hallo or hi is normally a short mew, just return the greeting with a pat or some reward. If your cat really wants something, it will unleash a long but not scary growl, you should definitely go where it is to find out what it needs. In case you cannot deduce what it is it wants, offer it something like food, water or some treats. If it persists, give it some scratch down or pet it, if that works, expect some cuddles in return.