One of the keys to making your Mac run smooth is by keeping everything up to date. This does not only go for your system software but for all other applications as well. Updates usually provide bug fixes, stability, compatibility and performance improvements. There are a few ways of checking if all your applications are up to date but we will cover the quickest ways.

1. Software Update - Apple's own updater. If it's not set to automatic check (it is by default) then try to manually activate it once every 2 weeks to make sure you have the latest system, Mac apps and security updates.

2. Other updaters - Most bundled software (Adobe, Office etc.) comes with it's own updater. These can be set to check for new updates automatically and will inform you when new software is available.

3. The rest - For all the other applications, plug-ins, add-ons etc. there is a very handy application called AppFresh. It will scan your entire system, find all your installed applications, and checks online to see if there are updates for them.
For more information on AppFresh visit this link.

The above 3 options will cover 99.9% of all your software that can possible need an update. Before updating any application always make sure you have a good backup of all your data and try to make it a habit to run Disk Utility's Repair Permissions command before and after updating. A restart after all the updates are done is also recommended even if an updater doesn't ask for it.