Shooting in manual mode?

So i have a nikon D3100 and have never shot out of auto mode i'm scared i'm wandering if i can get so tips about starting to shoot in manual thinks

I would start with reading your manual and learning how to use the light meter that is built into your viewfinder. Once there you will need to learn which aperture you should use for a desired effect and which shutter speeds you should use for a given effect or to freeze action. I suggest you buy a book called Understanding Exposure by Bryan Peterson to get you started. A class in basic photography would also be good.

While you're at it, look up the, 'Sunny 16 rule.'

You should be shooting in AV mode or in some situations where Shutter speed is most important, use TV mode.

When I bought my first "real" camera, a Minolta SRT-100 35mm SLR, in July of 1971 the first thing I did was read the Owner's Manual. I had no choice but to learn to shoot in Manual since that was the only option. If I didn't physically set the correct shutter speed for the aperture I wanted to use or physically set the aperture for the shutter speed I wanted to use the exposure would be wrong. If I didn't physically set the ISO of the film I was using the exposure would also come out wrong. I didn't really know it at that time but I was learning about the Exposure Triangle. You need to do the same - learn about the Exposure Triangle. This site will teach it to you:

http://www.digital-photography-school.com/learning-exposure-in-digital-photography

Watching this video tutorial will also help you learn to use your Nikon D3100:

http://www.nikondigitutor.com/eng/d3100/index.html Who better than Nikon to teach you to use your Nikon D3100?

I also suggest spending time at these sites to further your photography education:

http://www.photographymad.com/pages/view/10-top-photography-composition-rules
http://photographyknowhow.com/photography-lighting/
http://photographyknowhow.com/quality-of-light-in-photography/
http://photographyknowhow.com/direction-of-light-in-photography/
http://www.luminous-landscape.com/columns/aesthetics-1.shtml

Why scared? Just put it in manual mode and start taking pictures. Tweak each setting and see what it does. Eventually you'll get used to it.

You can take a picture of something in Auto Mode (without flash), then look at what settings the camera chose. Choose the same settings and take the same picture again. You will see that it looks the same. Now change the shutter speed up or down and see what it does. Do the same with aperture and ISO. Read your manual to see how to change those settings. That way you'll learn what the settings do. The light meter in your camera is gonna help you find the right exposure.

And agan, just shoot. There's nothing to be afraid of. If the picture comes out bad, tweak the settings till it looks good. It's all about practice.