To achieve better search results and add only highly targeted tweets to your Twitter feeds, you can use standard Twitter search operators. 

If you wish to search for tweets that mention a specific keyword, simply specify this keyword or phrase in the text field in the Twitter Feeds Basic settings:

A separate feed will be generated for each specified keyword.

If you wish to search for tweets that mention at least one of the targeted keywords, you can use OR operator:

To search for tweets by several keywords you can also use Advanced search. Specify your main keyword in the Basic settings (keyword 1), and other targeted keywords (keyword 2, keyword 3) in the Advanced setting in the Filter by keywords option. You will get tweets that mention at least one of the specified keywords:

And you can filter out tweets that mention a specific keyword in the Advanced setting in "Filter by negative keywords".

If you wish to search for tweets that mention several keywords at a time you can simply specify your keywords in a single search string using space or "+":

If you wish to search for tweets that mention an exact phrase, use quotes ( "keyword 1 keyword 2"):

You can also search for tweets that mention a hashtag or a Twitter user:

Here is the full list of standard Twitter search operators: