A solid bottom-end is often desired in a finished mix. Intuitively, adding more bass EQ seems natural, but in fact this can fill the low frequency range, leading to muddy, indistinct bass. Set Band 1 to Hi Pass filtering (its default mode) and remove frequencies below the useful range of an instrument's frequencies. There may be little audible change, but even an electric bass and kick drum can benefit from removing ultra-low frequencies, below 40 hertz. The cumulative effect across a mix can make a big difference in clarity.
Identify how a sound requires improvement and consider how to achieve this by removing frequencies, rather than adding. Results from subtractive equalization tend to sound more natural. Any equalizer can be thought of as a series of amplifiers, each operating in its own frequency range. When you boost a frequency, you also boost noise. Again, on one track the effect may not be noticeable, but this is a fastidious engineering practice which pays off on complex, multi-track projects.
A parametric equalizer such as Sonitus is a handy tool for pinpointing problem frequencies on a track. If a particular sound has a component you want to remove, select a band and Peak/Dip filter. Use a narrow Q setting by raising the value, and boost that band extremely, so the graph shows one sharp spike. Sweep the frequency of the band to accent the range you wish to remove. There will be a point where the offending frequency sounds most obnoxious. This is the point where you want to set the frequency, reverse the boost to a cut, and adjust the Q to alter adjacent frequencies to remove the problem.
From Track View in SONAR, Sonitus can be activated on any audio track. Note that if you are using a virtual instrument with a MIDI controller track, you can perform audio equalizing from its accompanying audio output track. Click on the circle to the left of "EQ" or double click the small graph window to open the full Sonitus dialog box. Note that by holding "CTRL" while selecting bands, you can group more than one band together. Adjustments to one will be made to the others in the group as well. Hold the "Shift" key on your keyboard as you click on a band to change the Q parameter.