Despite your best efforts, your Mac is running a bit slow. Hard disk space is filling up fast and applications are getting sluggish. Don't worry too much, it happens to everyone.
While there is no definitive cure-all for making your machine as good (and as fast) as day one, there are some basic things you can do that might help reclaim disk space, remove some clutter and generally speed up your Mac.
Follow this link from wired.com for helpful tips
(thanks to lil blacker for this tip)