Melting Asphalt's A Nihilist's Guide To Meaning is a good guide to what constitues a meaningful event.
It proposes that since events cause each other, an event has higher meaning to us if the event is more of a bridging point: the event was crucial or else a lot of other events would not have happened. An event is less meaningful if it's a dead end - it didn't cause many events afterwards.
This is an interesting perspective to view meaning through. If we want our lives to be more meaningful, it could mean that we need to become a part of the chain of events and start more things that would not have been started otherwise.
What is the meaning of...
Crisis of meaning
Upon reaching a ripe old age, many people experience some garden variety of existential crisis. They ask questions pertaining to the meaning of life, or the universe, or their work, and sometimes feel incredible sadness when they cannot find any.
I argue that what it means to have meaning is not well defined in those kind of questions. Looking at a human being and asking - "What is it's meaning?" - yields the same results as looking at a pile of kindling and asking what it's meaning is. What atually is the meaning of kindling? Does the kindling have no meaning? Say a traveller gathers the pieces of kindling and adds them to her flame for warmth on a cold night. Is the meaning of the kindling to be burned? I argue it is not. The meaning of kindling is whatever we say it is - we assign it a meaning just like we assign things a value or a name.
Asking an opaque question like "what is the meaning of X" implies meaning is some property of every object. I would assert that there is no such thing as meaning, and meaning cannot be measured, inquired as to, or compared, unless you're building a narrative, where you simply assign meaning as you see fit. The real world pays no attention to the need of humans for their lives to be organised into narratives, however, and so meaning is simply not applicable to reality. Many mistake the fact that there is no meaning at all with the idea that their lives are meaningless. Their lives would be meaningless only if some other person's life was meaningful - if there was some actual property of meaning floating around in space. In actuality, the idea of meaning is contradictory and bizzare, and the answer to "what is my life's meaning" is not available, and it is a mistake to be either upset or happy about that fact.
At least in my sort of existential crises, I find that usually it's just usually a far simpler emotional issue present that I am accidentally ignoring, which sometimes manifest in sad philosophical musings. Since I realised that, I have far less concern with any sort of philosophy which pertains to our existence or meaning or lack thereof.