Learning the blues scale and blues licks are great ways to dive into the art of improvising guitar solos. But learning the scales is really the easiest part of learning to solo on the guitar. Notes and licks can be taught - what can't be taught is the ability to inject the feeling that really good guitarists manage to convey in their guitar solos. Conveying emotion in your solos can be learned, but is best learned through repeated listening to the solos of your favorite guitar players.
One of the things that new improvisers invariably do is try to play far too many notes in their guitar solos. The key to a great guitar solo often lies as much within the space between the notes as it does with the actual notes. Perhaps the greatest example of such an economic approach can be found in the guitar solos of the incomparable BB King, whose improvisations rarely include fast runs of notes. King often spends as much time not playing during his solos as he does playing notes. Think of his approach this way - he's got a great (hopefully) band playing behind him. Even without his solo over top of them, the music sounds great, so any notes King plays are an added treat to make things sound even better. For more insight into the style of King, read the Learn to Play Like B.B. King.
Try utilizing this sparse approach - play a guitar solo along with any 12 bar blues you have a recording of, or with the 12 bar blues audio clips found on this site. Focus on sounding good while using as few notes as possible. Try playing the same note repeatedly - perhaps only using one note for an entire 12 bars. If something sounds good (or bad), analyze and memorize what you played, so you can play it (or not play it) again. Solo along with your favorite guitarists, and try to emulate the feeling (not necessarily the notes) that they convey when improvising.
Another way to make your guitar solos sound more effective is through the use of several guitar techniques. "Note bending" can add a very expressive quality to guitar solos. Playing the note A on the 10th fret of the second string, for example, will give you a particular sound. But playing the note G on the 8th fret of the second string, then quickly bending up to the note A and holding it can add a nice color to the note. Techniques like string bends to create different sounds are extremely valuable when playing economically - bending and holding one note can sound great, as opposed to playing ten notes quickly. To learn more, read this lesson on note bending.
One of the most important techniques guitarists should have a firm grasp on is the ability to use various types of vibrato. Playing and holding a note without adding vibrato can often result in the note sounding "dead" - like it's just sitting there, doing nothing. Take the time to listen to all your favorite guitarists - notice that they almost always use vibrato, especially when holding a note. In this lesson on vibrato, several types of vibrato are explained and analyzed. Utilization of vibrato will again make sparse soloing more interesting for the listener.
If you've plowed through this material, and are still itching for more, here are six other ways to improve your lead guitar playing. Good luck!