In this article, I assume that you have some familiarity with the blues scale and are starting to use it to improvise phrases over a 12-bar blues pattern. That's great, but you're not sure how you can go beyond randomly playing notes to create a solo that will really blow people away? Killer guitar solos are about more than playing notes from your chosen scale aimlessly all over the fretboard! So, to help you out I've prepared a few pointers to how you should think about what you're playing when improvising a solo:
Chord tones are really important to focus on when you're soloing, particularly the root notes (the chord tones are the notes that make up the chord that you're playing over). These provide the strongest resolution points, so phrases that start and end with chord tones will often sound better. Start with the root notes, and for each chord in the 12-bar blues pattern you are using practice playing phrases that start or end (or both) with the root note. If you're comfortable with root notes, move on to phrases starting or ending using other notes in whatever the current chord is.
If chord tones are strong resolution, then why not use phrases that are all chord tones? These are arpeggios - the notes of a chord played separately - and they can sound really good used judiciously in your solo. Practice playing arpeggios over a 12-bar blues backing track and then use them within your solos, mixed up with other phrases.
A very important musical concept is repetition, as familiarity is appealing to listeners and solos with good use of repeated phrases can sound more thought out than free flowing solos. Here are a few ways that you could incorporate repetition in your solos:

• There's nothing wrong with just playing a lick and repeating the same lick a few times, particularly if the chord changes underneath it - this can sound really great if used well.
• You can play licks with the same rhythm, but using different notes to keep a consistency in your solo
  Another approach is to play licks using identical notes, but with a different rhythmic structure. You may find this more difficult to achieve, but stick with it as done well it can add some nice elements to your solos.
• Even just playing the same note or double-stop repeatedly can sound great in the right place in a solo. A good pattern is to play triplet notes, maybe sliding or bending into the first note of each triplet. Listen to the great guitar solos by players such as Chuck Berry to hear how this can be done well.
• Often in blues, players use question & answer phrases in their solos. To play these, you play a "question" phrase followed by an answer phrase. The question is usually repeated, perhaps with some variation, with the answer improvised more freely. To play this in a solo, try playing the questions low down and the answer higher up. Or even better, play with a friend where one of you plays the question and the other plays the answer. Try coming up with a low "question" phrase using the blues scale. Play it and then follow it with an answer phrase played higher up the scale. Play these repeatedly, improvising the answer phrase freely, over a 12-bar blues backing track. Introduce small variations into the questions once you start to get into it.

Well, there's a few ideas that will hopefully make your blues solos sound more professional. Now you can practice incorporating them into your practice sessions as you continue to learn blues guitar!