You don’t need to take everything off and do a clean install, but it will help a little. Can I suggest the following;
How full is the hard disk ? The fuller it is the slower the machine will run especially if the RAM is being fully used. You can check disk usage on “About this machine” under storage. Delete old stuff you don’t need, this includes old emails and attachments, inbox and sent items. You can spend a couple of quid on “disk doctor” in App Store – it does some useful things but make sure downloads directory is empty and/or only has files you need (best to move them elsewhere). Clear/empty the Trash. You can run Activity Monitor to check ram usage. To be honest if disk isn’t full this housekeeping doesn’t matter.
RAM – more is good, I had a 2009 MacMini with a full hard disk and 2gb ram and it ran really slow. It now has 8gb RAM and 750hdd and runs really fast. Unless you are running graphics/viedo editing your machine will run OK with 4 and great with 8. I added my ram and new hdd myself. Online guides. Online sellers (I bought Corsair RAM and Western Digital 750gb 7200 rpm drive – cost about £125 I recall). You can pay for others to do this for you. Doing it yourself invalidates the warranty but if machine is 2+ years old that doesn’t matter
OSX (operating system) – I would definitely recommend upgrading to Mavericks (10.9) – it’s free and has many improvements inc better memory management. Ideally make sure the hard drive is cleaned first and you must have a backup. An external drive is £50, worth buying for backups (very easy with TimeMachine) and very useful anyway.
Note if you are going to upgrade hard drive (more capicity) or speed (a Solid State Drive SSD) you will want an external drive for backup, you can buy a cradle into which you can put your current hard drive and then can then be you backup device.
MacRumors is a good website with active and helpful forums
How much RAM do you have, how big/full is your hard drive, what OS are you running ? Answers available from about this mac under the Apple Logo menu.
My email is in my profile – ping me for more info
EDIT: Just seen your posts – 1 year old macbook pro should run pretty sweetly (it must have 4gb ram min and 500gb hdd ?). What have you installed on it ? I’ve seen things like dropbox and googledrive slow machines down due to speed of online file synching especially if wfi is slow. You MacBook Pro is much more powerful than my MacMini which runs fine.