A few points

I think, if you want to take full advantage of twitter for learning and networking, there are a few things you need to know:

• Twitter is a tool. Its neither the solution to all your problems nor the end of humanity as we know it.
• Don't care about global trends, care about relevant ones.
• Spending time on it is good, even if its about a few hours a day, just make sure that you're getting useful information out of it.
• Don't get dogmatic about following people. Follow anyone and everyone that is relevant to what you're learning.

The Pulse

One of the first things I did when I started using Twitter is that I started following the people relevant to what I was learning. In the Python community, there are plenty of people who are relevant like Guido Van Rossum or Alex Martelli. What's more important is these people also followed people who were relevant in their own communities. So, I started learning about guys like Raymond Hettinger and Donald Stufft. So by following Raymond Hettinger I knew about Wesley Chun, who wrote "Core Python Applications", a book that I never knew about before.

Trends

The reason I'm talking about all of this is that Twitter can be an excellent tool when it comes to understanding and exploring a community, as well as the hierarchy of the community. But there's more.

If you know all the hotshots of a community, it doesn't take much to realize that their collective voice is pretty much the pulse of the community and that tells you about how its doing. Recently, there have been a lot of people in the python community avidly following the happenings in the go community as well. Top programmers have started following Rob Pike and go specific twitter accounts.

So, that tells you something. Golang is going places.

Getting Help

People respond more willingly on twitter. It takes very little effort (compared to an email) to send a tweet. Its short and sweet, so if you want help with something, ask on Twitter.

Hashtags

Don't abuse them. People will start blocking and ignoring all the crap you're talking about. Make connections, and do so earnestly; don't waste other people's time and screen real-estate.