Blues clichés, although sometimes boring and predictable, are a valuable asset to your musical vocabulary.
Before you can break through the boundaries of pentatonic scales and repetitive 'over used' musical ideas, you need to have a good understanding of the style to begin with. Knowing the common cliché's is the first step to achieving this!
Let's start with a classic blues introduction. Often played on guitar or piano, this riff has a strong sense of resolution. With the slightest tweak, this riff can be effectively used as an intro or an outro.
Example 1: Gives us a 4 bar introduction type riff, no doubt you would have heard something like this before. The intro ends at bar 4 on a D7 chord which hangs for a couple beats desperately wanting to resolve. For this example we will resolve to the G7 and begin our song.
Example 2: This is basically the same riff only we resolve straight to the G7. Listen to it, it has much stronger sense of resolution. It doesn't feel like it needs to go anywhere else. Perfect for an ending.
Example 3: Another way to approach the last 2 bars of Example 2. This can also be used as an ending on its own.