Chapter 10 in the Miriad Users Guide has an extensive discussion on flagging your visibility data. The two important programs that allow you to interactively flag are uvflag and blflag.
Programs such as uvplt and varplt can be used to inspect data and decide what baselines, antennae, time-ranges etc. need to be flagged. Another potentially useful way is a relatively new program uvimage which creates a Miriad image cube out of a visibility dataset. This 3 dimensional dataset can be viewed with programs like ds9 or karma's kvis, and guide you how to flag the data using uvflag. It is possible to come up with a procedure that ties keystrokes in ds9 to the creation of a batch script that runs uvflag afterwards, and this is a likely change in upcoming versions of MIRIAD.
% uvimage vis=cx012.SS433.2006sep07.1.miriad out=visbrick1 UVIMAGE: version 22-dec-2006 Mapping amp ### Informational: Datatype is complex Nvis= 95628 Nant= 13 Nchan= 90 Nbl= 78 Ntime= 1226 Space used: 8606520 / 17432576 = 49.370327% number of records read= 95628 % mirds9 visbrick1
The most useful output mode is amplitudes (the default) where the cube will be constructed with channels along the X axis, baselines along Y and time along Z. The X axis is represented in ds9 by different planes in ds9). As you move the Data Cube slider you will see different channel-baseline images of the visibility amplitudes at different times. Look for a change in noise, regions of pure 0s, vertical spikes (a.k.a. birdies), horizontal spikes (bad baselines or antennae). These will potentially all have to be flagged. Overall noise increase that is the result of a higher system temperature will be accounted for though (see invert).