The first thing to check for is if your system meets the minimum requirements for the game you are trying to play. If it doesn't, find out what you need to upgrade and contact our support team. If you do meet the minimum requirements but only barely, then you may want to consider lowering some in game settings such as Anti-Aliasing (sometimes called FXAA, MSAA, SSAA, or CSAA), lowering textures and shadows, reducing draw distance, etc. The game won't look as nice, but the tradeoff will be much better framerates.
If you are well above minimum requirements and it still runs poorly, then there a few other steps you can try to determine the issue. If you have an Nvidia card, Nvidia sometimes releases an optimized driver for some games (especially AAA titles). These can greatly improve performance. You should definitely check the site for your video card (Nvidia or AMD) for the newest drivers.
If you have an SLI setup and your games run poorly, the issue may be SLI itself. While SLI can potentially double performance, in many cases it only offers marginal gains, and may even hamper performance. A game running well in SLI depends on whether the game supports SLI, if it is coded well to handle SLI, and if Nvidia has released an optimized driver. It is not uncommon for a game to run better on a single card, even in an SLI setup. If that is the case, you can temporarily disable one of your cards through the Nvidia Control Panel.
One other thing to keep an eye on is system temperatures. If the system is running too hot, it will slow down the CPU and GPU to cool down a little bit, but that takes away from performance. To check your temperatures, download a program called HWMonitor and leave it running in the background while gaming. Periodically use Alt+Tab to switch between the game and HWMonitor. HWMonitor shows a lot of information, but the two things to watch are your CPU and GPU temps. If the CPU or GPU is getting close to 90C or higher, then it is definitely too hot. If that's the case, then pulling off the side panel and looking to see if there is any dust buildup on the fans for the video card or CPU is the next step. If there is blockage, then use a can of compressed air to clear it out.
If none of the above seems to help, the last step is to determine if the issue is a single game or the video card itself. If only one game is running poorly, then that game is most likely the cause. At this point there isn't much that can be done other than waiting for an update to the game or a newer video driver. If the issue is persistent across several or all games or 3D intensive applications, the issue may be the video card. Download a program called GPUTest and run it on your system. When the program is open, check the box that says "Enable OSI (On screen information) and then choose the appropriate resolution for your monitor. Don't worry about setting anti-aliasing. Finally, click "Run stress test" and let it run for an hour or so. Things to watch out for are any kind of screen tearing or artifacting (unusual pixilation), screen turning black and then coming back on, Blue Screens or complete shutdowns, or system lock ups. If you experience any of these issues, give our support team a call and they will assist you further.