A "Hello, World!" or "Time to Hello World" event generally is a peer-2-peer event that helps to meet other people in an organization. Such an event is very simple and easy to organize in most organisations and is used to make easier the basic networking activities of new peers. It is often one of the first events organized by new-hires learning the new network structure. This is one measure of an organization’s culture and openness; since the event is meant as an introduction for people unfamiliar with the organization, a more difficult "Hello, World!" event may indicate that the organization is less open and less network-based.
It can help you to extend the on-boarding in the organization, grow your network faster and thanks to this have better work experience.
Use your intuition and discipline. You are in a meeting, discussing whatever and you noticed a person talking about things important or interesting for you. The person seems to be interesting or impress you or whatever reason algorithm-of-your-choice you apply.
Without thinking too much and analyzing pros cons should I or shouldn't I? ... you just send an invitation to "Hello World!" meeting explaining you want to meet this person, have a small talk, talk about a special subject (depends on the situation), whatever.
Every time you feel or see this spark you repeat the process....Do not create a To-Meet-List just send the invitation and let the network grow. The key is to do it again and again, contacting new people again and again, never stopping extending your network including new people continuously.