Rather than write a long "how-to" guide, I'll let the videos on YouTube do the talking for me...
1. iCleaner (BigBoss repo)
This Cydia app clean up all the unnecessary & temporary files built up over the months/years. Running it will free up some space and speed up your iPhone. I recommend running it every month or two.
2. Speed Intensifier (ihacksrepo.com or repo.insanelyi.com)
This tweak simply speeds up the animations on your iPhone making it feel faster. The setting on my iPhone 4S for this tweak is +6 as I find it provides a good balance between animation and speed.