Start with gain staging: high-pass everything except kick and bass around 100 Hz to clear mud, and leave 3–6 dB of headroom on the mix bus for mastering. Aim for peaks around -6 to -3 dB before you master.
With EQ, cut before you boost — subtractive moves sound more natural. The amateur-mix killer is frequency masking: two sounds fighting for the same range. Fix it by carving space with EQ (usually cut the less important element) or by sidechaining.
Keep kick, snare, bass and lead vocal centred and mono below ~120 Hz; let hats, percussion and synths roam wide for stereo width.