A trill is a rapid succession of hammer-ons and pull-offs, with only the first note being picked. The trill is indicated by the symbol Y above or below the two notes concerned, with the first note being shown as a grace note.
Listen to the following example on the CD to hear the effect of the trill.
Here is a lick which makes use of the trill. Experiment with adding trills to some of your own licks.
To finish this section, here is a solo which uses most of the rhythms and techniques you have learnt up to this point. Pay particular attention to the notes in bar 6, where a bent note is held and picked repeatedly. Take the whole solo slowly until you can comfortably play all the notes, then memorize it and practice it along with your metronome. Gradually increase the tempo over time until you can play it along with the recording.