Download and install EVGA Precision if you haven't already. This guide assumes you're using Precision. Also download and install FurMark. Precision is used to overclock and FurMark is used to test for stability. There are three clocks that can be adjusted: core, shader, and memory. By default, your shader clock is linked to your core clock. When overclocking the core, leave the shader linked to the core for now. Increase the frequency by 5-10 Mhz then use FurMark to test stability. When using FurMark, set everything to maximum and make sure you select 'Xtreme Burning Mode'.  Look for artificating and other graphics anomalies (random sharp or triangular lines appearing and/or disappearing at random or random white checkered patterns). Run that for about 5m. Make sure you keep a close eye on the temperature. Make sure the temperature doesn't exceed 95^oC. I say 95^oC just to be safe. According to NVIDIA's website, the max. safe temp. for your card is 105^oC (click here to see spec page).

Keep increasing the core by 5-10 MHz (with shader still linked) until you start seeing graphical glitches in FurMark. Once this happens, unlink the shader clock. Back the shader clock down about 10-20 MHz, but keep the core where it's at. Test it out. Keep backing the shader clock down in 10-20 MHz increments until the glitching stops. If you're still seeing glitching after you've lowered the shader clock down about 50-60 MHz, start to decrease the core clock by 5-10 MHz, but leave the shader clock speeds where they are. Repeat that process. Eventually you should reach a stable frequency for those clocks. Be sure to keep an eye on the temp while you're overclocking, especially when your core clock is 50 MHz+ from the stock speed.

The memory clock is fairly simple to overclock. When you overclock the memory clock, be sure to reset the core and shader to their default speeds, but be sure to keep a note of the stable frequencies. Increase the memory clock in 100-200 MHz increments. Use FurMark to test. You'll know when you've pushed your memory clock too high when your screen fills with either millions of tiny dots or many tiny square boxes. Just like the core and shader ocing, if you see any graphical glitching, decrease the speed. For the memory I recommend decreasing in 100 MHz increments. Your computer may hard lock if you've pushed the memory clock too high. If it does, manually restart it immediately. Also, when you adjust the memory clock, NEVER EVER select "APPLY AT WINDOWS STARTUP." Only select that when you're positive ALL the clocks you've tested are stable. Always write down your speeds and findings while testing in case your computer crashes.

When you've got all your stable clock speeds, run FurMark for about 20m. After about 5m, you should see what the maximum temp. is for the test. You'll know when the temp. doesn't increase anymore.

Just keep an eye on the temps during ocing and make sure they don't exceed 95^oC. If they do, just end the stability test and back the clocks off

 Thank You XrayMan! You anticipated all of my questions!!!! 

 just to be safe I think I will leave core and shader here (740/1644)
6 minute furmark test hit 94C with no artifacts...I will now reset these to factory and start messing with the memory...will keep informed of results...one more quick question. You said everything maxed out on furmark. Does this mean screen resolution as well? So far I have just been using 1280 X 1024.
 
edit...wow...this card does not like the memory increased by much! From 900 to 1000...test ran stable. When I increased to 1100 the desktop started glitching before any test ran!!! ! I quickly shut down without applying at startup!

OK THANKS AGAIN! Think I will just do further testing on Core and Shader and leave Memory clock alone!

Better now...added one more case fan. now 750/1666 and temp maxed out at 83c!