Is it worth keeping your computer on to mine Bitcoins/Litecoins? Is there a most effiecient/fastest way to mine Bitcoins/Litecoins? I also own an Nvidia GeForce 560ti (MSI) GPU.
The only way to be cost-effective right now with litecoin (the bitcoin ship sailed long ago) is with Radeon HD 7xxx or R9 cards and even then, they're only profitable if you're not paying for electricity.
At present, ASIC/FPGA is the fastest and most efficient hardware for mining. It has no guarantees actually. Bitcoin and Litecoin mining can either make you a millionaire or it will cost you much time, money and effort. Best of luck to you!
The only way to be cost-effective right now with litecoin (the bitcoin ship sailed long ago) is with Radeon HD 7xxx or R9 cards and even then, they're only profitable if you're not paying for electricity.