With the release of Spirit now imminent, it would be a good thing to save your SHSH blob, in case you need to downgrade in the future. Saving your iPhone SHSH is very simple.
Step 1: Download Firmware Umbrella from here.
Step 2: Launch Firmware Umbrella and plug your iPhone in.
Step 3: Click “Save My SHSH” and wait for Firmware Umbrella to do the job.
Done! A copy will be saved to your computer and it will also send a request to Cydia to save your SHSH on Saurik’s server.