Troubleshoot/ Tune Android performance / speed
There are a bunch of Tutorials around on the net on how to increase performance of your Android device (e.g. on LifeHackers here and here). One thing to definitely keep your fingers AWAY from are so-called "boosters" and (automated) Task-Killers. As rm-vanda already stated, they make things only worse; tasks should only be killed if they misbehave (e.g. are hanging, running havoc while eating your CPU and the like). Android manages its RAM fine, no need to worry about that.

As for the auto-starters, I can recommend AutoRun Manager, which is actively maintained and simply the best of all I tried (and I tried a lot).

To figure out what is consuming your ressources, a good candidate helping you would be System Tuner. While the free version simply lets you monitor activity life, the pro-version also offers background-monitoring and stores its data for later analysis.

Some other steps you could perform include:


from time to time, clean up caches (to remove old data and get back precious internal memory; helping apps in this segment include Cache Clear, Quick Cache Cleaner, CacheCleaner NG, and Android System Cleaner - the latter taking care for more things than just cache
Moving some rarely used Apps to SD (if they don't have widgets you are using) saves additional internal space.
uninstall unused apps