If you really want to get into Twitter, you have to devote some time to it and it helps if there's some topic that you're really interested in and want to learn more about. If you "follow" people with a similar interest who use Twitter well, ie who post links to relevant/interesting articles or blogs, then you'll get something out of it. But it's not that intuitive if all you want is to post messages about what you're doing that day and you have no focus for what you want from other users.
Putting a # in front of a word makes it more easily searchable. #ff is short for #followfriday. This is a tradition whereby on a Friday, Twitter users share the details of other users they like, so if you want to recommend Mumsnet, you'd post the following: #ff @mumsnettowers [I think that's their username but can't remember].
But it's all a lot easier if you use Tweetdeck or Hootsuite or another 3rd party application that allows you to organise the people you follow more easily into categories, or according to the search term that you're interested in, eg photography.
I think Twitter is great for sharing info and finding niche articles you others would never come across. But unless you have some time to get your head around it, probably give it a miss. But it's not true to say that, just because someone doesn't "get" it, it's rubbish.