Replying to Anybody Have a Nikon D300s

I am making this thread to get some tips on shooting with the nikon d300s. i Have it all figured out for the most part. but some problems i have had is that i have gotten a lot of grainy footage when shooting in low light. i know my lens isn't helping that since its a f/3.5-5 but what are the best settings to use when shooting low light. also how do you manually change the shutter speed my canon was a lot easier to find and I'm having trouble finding it on this one? if anyone can help it will be greatly appreciated!