As Sten answered above, putting lists is the one way to attain your objective…
There is one more way that can resolve your problem: I am assuming that for the users in question, you may be interested in their tweets on some specific topics, perhaps some common areas of interest. But you are not interested in other topics from the same users.
Solution: Use the followers of your target-users as filters. In other words, instead of following the particular user, selectively follow followers of the target-user, who retweet the content of your choice from the target user.
This may sound confusing, so here is an example to make things clearer.
User X tweets on two topics a lot: web-marketing and Basketball, and you may be interested only in web-marketing.
To solve the problem in the example case above, simply locate the followers of User X, who are passionate about web-marketing. One or more of these users will surely re-tweet good web-marketing content from User X. So you will see whatever X says about web-marketing, without ever having to see a running commentary of a basketball game.