Compression.Limiting. Normalizing. Parametric equalization. Master volume if all else fails , which is almost never the case. It's all in the way you tweak your levels. Insted of boosting frequencies you want , you can cut the ones you don't want , then bring everything back to unity gain. Tweak each channel seperately. Give each instrument it's own effects channel. Never , ever , ever let that bar thing flash red.
*Summons Xelebes/Compyfox or equivalent in hopes that they can offer more extensive help*