Know the feeling when it comes to playing solos? Switch from sound being used for chords to sound which does have a bit more volume for your single string notes. Easy, change channel on amp! Okay, but usually this channel does have a different overal tonality, it is not just louder but also different in sound (and feel). All depends on your amp eh?
Let us say you use a one channel amp with a gain control to overdrive the amp. You can set your amp up for an overal, solid rhythm sound with just a slight bit of distortion on the edges of your note. When you kick in the EQ pedal it will give you a slight boost to create even more hair on the notes. Hopefully this slight boost will be enough to make your single notes come through in the mix of guitar, bass and drums.

What about using a dist. pedal to boost the sound? Yes, that is good as well, but usually the tonality of your sound will change. The EQ pedal trick will keep more of your original tone intact. You can set up the EQ pedal to boost the bass-or treble registre, all depending on your own taste. Usually a bit of treble will do to get a slight boost on your overal sound.

Before you think of EQ pedals or Dist. pedal or whatever, it may be also possible to change pick-up setting on your guitar to get a slight boost. Often this may be the best option, since it does not require any extras in between your guitar and amp. On most guitars, the bridge pick-up will get you a trebly sound which may be enough to get a bit of boost onto your sound. Try experimenting with your pick-up setting before you decide on using any extras. Have a look at how you set-up your amp, get the amp to work clean on neck pick-up while the bridge pick-up should give you a slight boost. In case your bridge pick-up is noticeably quieter, raise the bridge pick-up to increase its output level. Overal, your pick-ups should be balanced: You should hear a difference in sound when you switch from one setting to the next one, but one should not be quieter than the other one. You can quickly check the balance of your pick-up by playing any open chord (A will do for now) let chord ring while you change setting of your pick-up selector and listen to what it does to your sound.  

The boost approach I described above may be more for guitarplayers who want a subtle boost in their sound rather than a radical change in tone for their solos. Whatever you go for all depends on the music you play, your taste and experience.

Hope to catch you soon again,
Eddie