(He's doesn't mean being nudnik or getting in people's way with fake helpfulness, he means granting real assistance, even when it's not absolutely necessary.)
When Noach falls asleep after drinking a bit too much wine (in an effort to thank Hashem), his son Shem picks up a blanket and out of respect for his father's privacy, Shem walks backward.
Shem's brother Yafet reaches out to take hold of the blanket and also walks backward. Together, they cover their father.
Why would Yafet do that?
A blanket is neither heavy nor unwieldy. Shem could manage perfectly well by himself.
The answer is: Yafet wanted to be part of something worthwhile.
In return for Shem initiating this respectful act, Hashem decided that He will dwell in the tents of Shem.
And Yafet the tag-along ended up ruling the world until this day: Rome, Greece, Europe, Persia — they're all the descendants of Yafet.
How to Hitch Yourself on to a Mitzvah
Small things count.
As Rav Avigdor Miller says on page 8:
"When you take hold of the corner of the blanket and say, 'Me too!' it’s a demonstration of where you want to be; where your heart is."
Another example is giving tzedakah. Someone wants to build a yeshivah? Maybe you can't pay for all that. But maybe you can still give a few dollars/shekels/euros to show your desire to participate in erecting a house of Torah.
And this applies to many opportunities to give tzedakah (page 9):
"Whether they need your five dollars is not the question — even if they don’t need you, you need them."
Rav Miller describes seeing how Rav Aharon Kotler of Lakewood lived: very poorly.
So this increased Rav Miller's admiration of Rav Kotler because Rav Miller understood from this that all the money donated was definitely going to the yeshivah, and Rav Kotler was not pocketing it, even for his very real needs.
"Identify with All the Good Jews Everywhere They are."
For example, if you sit down at shiur (even if you don't understand it), you get reward for that because you're showing that you want to be there.
And even if you can't learn, just sitting next to people who are learning earns you merit.
Because you are showing God that you wish to associate yourself with Torah learning.
When you participate in a hachnasat sefer Torah (including that of another group), when you order a subscription for a frum newspaper or magazine to be delivered to the home of someone who doesn't know much about Torah Judaism (I suppose forwarding Aish videos and the rest is the modern equivalent)...you get reward for joining them even though you're not doing the main mitzvah.
And if you can't contribute physically?
Then at least contribute in your heart (page 13):
"Join in whichever way you can; but at least think in your heart, 'I am part of it.' And Hakodosh Boruch Hu gives you credit for taking hold of the blanket, for joining in with them."
If we had to sum up our lecture in one sentence we’d say that we must begin to join in with good people. As much as possible we try to be [nitipal l'osei mitzvah] to those who are doing good things.
And even though we ourselves sometimes might be far away from their perfection, we still identify with good ones as much as we can.
Now that’s a very important lesson.
Identify with all the good Jews everywhere they are.