Clean It Out
The first thing you'll want to do is clear out the riff-raff — unused programs and browser extensions, obsolete registry entries, and expired permissions. Uninstall unused and under-utilized programs on your desktop and laptop systems, clear out forgotten apps from your mobile devices (Sorry, Angry Birds Rio). Give your registry a scrubbing with CC Cleaner, a free program for both Windows and Mac, that will clear old registry entries (for PCs) as well as empty recycle bins, zero out recent document lists, and erase a variety of browser information — temporary files, history, cookies, download history, form history — from the major browsers.
Also be sure to take a look through your browser's extensions list and remove any rarely used features. The same goes for Google users: Go to your Google account's security screen, select the "Connected applications and sites" option from the bottom of the list, and nix any old devices that you no longer own or operate.
Windows owners would do well to invest in a defragmenting program beyond the native OS offering. Defraggler, from Piriform, the makers of CC Cleaner, is a solid option — even the free version — for defragging all or just parts of your hard drive. Mac users, while not needing a full-feature defrag tool, will still benefit from DaisyDisk. This visualisation software displays the relative sizes of files across the drive, allowing you to quickly spot and eliminate corpulent documents.
And whether you're running a Mac or a PC, Android or iOS, make sure the OS is up to date and install any queued system or security revisions recommended by the system's auto-update program. For mobile devices, be sure to update all of your on-board apps as well.
Lock It Down
Once you've tightened up the OS and toned your system's basic performance, it's time to boost its defenses. Update your firewall and antivirus software. I'm a huge fan of Vipre but AVG, Norton, Kaspersky and a slew of other developers offer programs with varying degrees of service, features and pricing. Once updated, run the fullest, deepest, most complete scan your program offers, making sure to scan any attached external hard drives as well. For an added layer of protection, especially if your anti-virus suite doesn't already do so, install and run a Spyware Removal tool such as SpywareBlaster.
Your Android-based mobile devices are not to be excluded from the security sweep either. Both Avast and AVG offer quality mobile anti-virus services — basic features are free, advanced options like the Lost/Stolen Phone Locator/Eraser features will cost cash. iOS users don't need to take this step as their mobile devices are protected by a cloud of smug that no digital virus can penetrate.
You'll also do well to look into investing in a password manager — at least one that doesn't involve Post-Its surrounding your monitor. One Password by Agilebits is a very popular program as it allows users to manage and sync their password menageries across every desktop and mobile device — Mac, iOS, Android, or PC — using integrated Dropbox functionality for a one-time $US50. What's more, it also manages sensitive online shopping data, credit card numbers for example, as well.
If that's too steep for your security requirements, at least audit your list of passwords to ensure you don't have any duplicates and that your phrases are strong enough. Remember, an easy mnemonic like "If it's going to be that kind of party" is infinitely more difficult for a computer to guess (and easier for you to remember) than any combination of letters, numbers and characters you can devise.
Back It Up
Now that you've cleared away all the OS detrius and plugged any security leaks, it's time to take a snapshot of the system for posterity — and for the next time your system randomly decides to catch fire. Both desktop OS include native backup support to secondary storage devices — either an external hard drive or recordable media. Make sure you back up your family photos, documents, home movies, naughty movies and anything else you've either collected or stored on your computer.
While you can (and should) set an aggressive weekly schedule for this method of backup, it cannot provide the always-on protection afforded by online backup services, nor does it guard against larger crises like, say, a fire that destroys not just your laptop but the backups as well. Online services such as Carbonite and Backblaze, instead tuck your data safely away in the cloud while allowing for easy file transfers (a la Dropbox) between your machines and mobile devices. These services do however cost money — both Carbonite and Backblaze charge $US50-$60 annually to hold on to your data, for example — and offer differing layers of service so make sure to examine all your file security options before opening your wallet.
Wash It Off
Now that your devices' insides are squeaky clean, it's time to give them a thorough physical cleaning as well. Wipe down your monitors with a damp cloth, clean the gunk out of your mouse (if you don't yet use a laser mouse) and wipe off your desktop tower and laptop exterior. Shake out and vacuum your keyboard, scrub the keys with a mild soap and water solution to remove oily build-up and remnants from the latte you spilled in there last week. If you use a desktop tower, now would be a good time to open the case and blow out any dust bunnies out of the fans.
Congratulations, your computer, nay, your entire personal digital ecosystem is now fit as a fiddle and ready for anything the internet (and your perverse taste in backwater porn sites) can throw at it.