It may be tempting when you pull up an EQ to start boosting things like the thump of the kick or the sparkle of a vocal; however, you'll achieve much better results if you start by cutting out bad frequencies before you start boosting any frequencies.
By removing things like muddiness, boxiness, or harshness, you'll notice that your mix sounds cleaner, fuller, & naturally begin to sound brighter.
When you start by cutting first, your decision making will be better when it's time to boost frequencies.
For example, if you're mix is lacking brightness, instead of boosting the highs on a vocal or lead track, you may find that cutting some mid-range washiness on a pad or piano track will clean up the mix.
This could make your vocals sound brighter naturally by creating more room in the mixing spectrum.