You can filter off everything below 75 Hz (ish) if its in standard tuning, will generally just be mud and a bit of air. Boxy/boomy frequencies come in to play around 200-400Hz. To give it a bit of bite have a play around 2.8k and to brighten things up try around 5k - watch you dont make it too harsh though. Also, try different layers of different tones (ie) clean, crunch, overdrive, super overdriven. See if you get a balance between them you like better. Hard panning is also good when using layers for creating a big feeling of width.