There are 3rd party programs of course, but what I would suggest is the following.
(Use the spotlight search to find Disk Utility quickly)
Verify Disk and Repair Disk Permissions in Disk Utility.
If it still goes slow after Repairing Permissions and Verifying Disk, try:
Boot up into Safe Mode
Actually, your iMac is a 2010 model if it has a 3.06 GHz CPU.
Do you run any kind of AntiVirus software?
Open OS X System Preferences Pane. Locate and click on Accounts.
A Window should open. On the left select or click your user account. On the right click the Login Items tab to see if there are a lot of background apps or processes running in the background at startup.
Also, in your Home folder/Applications Folder, locate the Utilitites Folder. Open this folder and look for the Activity Monitor app.
Launch this app and look at all the processes running to see if you can see one or more processes that are taking up a large percentage of your CPU power.