#1 Play it safe when upgrading components in your computer.  Most big box brand computers are built with power supplies that are barely adequate for their current configuration.  Adding additional drives, memory, performance video cards, etc. can put a strain on you existing power supply.  It may be feasible to upgrade the power supply as well along with your planned upgrade.  Blue Moon Computers sells power supplies ranging from 400W to 1000W with various features (SATA connectors, PCIe connectors, SLI ready, multiple fans, fan controller, modular connections etc.)  Also, wattage isn't the only factor to consider.  Make sure that the power supply has sufficient amperage to support the connected peripheral (especially with video cards and the PCIe/12V power connector)  A good link to help you determine an adequate power supply for your rig can be found here:

http://extreme.outervision.com/psucalculatorlite.jsp

#2  Back up your valuable data!  With the low cost of USB flash memory drives and external hard drives, you have no excuse not to back up data that you consider "critical".  Whether this be family photos, music files, work documents/databases, etc.; a regular backup regimen would be prudent in preventing permanent data loss.  I consider myself an expert at data recovery from failing drives and media.  That being said, there are a few times where I am not able to recover a customer's data and I refer them to a Data Recovery Center.  Analysis fees alone range from $200-$500 and are typically, non-refundable.  Data recovery, if successful, can range in the thousands of dollars for even a few gigabytes of data dependent on the damage severity/length of recovery process.  Blue Moon Computers sells external hard drives, USB flash drives and offers off-site data storage (on our secure servers) to suit your back up needs. 

#3 You may love Fido, but Fido may not love your computer!  Remember to keep you notebook computer, phones, cables, media, etc. out of your pet's path or there could be dire consequences!  You would be amazed by how many walk-in repairs are due to pet damage.  Dogs that chew A/C adapter cords, parrots that peck the keys off of keyboards (this seriously happened :-), mice that manage to get into computer towers and chew wires, cats that "mark" the tower as their own, etc!  Also, an occassional air dusting of the computer's fans/fan ducts would be advisable if your equipment is located in an area with heavy, loose pet hair flying around.  Unplug your equipment from A/C power first in order to prevent damage.  Blue Moon Computers sells canned air duster, electronics cleaner, wipes, etc. for your convenience.