Signature Making for Beginners

BLACK AND WHITE WITH BITS OF COLOR

There are a couple ways to do this.  Since you're fairly new to Photoshop, I wrote instructions using the eraser method rather than venturing into the world of masks.  I hope that's alright.
 
1. Open your photo and do any editing that you’d like and resize if necessary.

2. In the Layers Palette (bottom right corner) right click on the photo and duplicate the layer.  Repeat.  Now you have three copies of the photo all stacked on top of each other.

3. Create a Hue/Saturation Layer by clicking on the icon that looks like a circle with half black and half white.  When the slider comes up, click and drag the meter labeled "saturation" all the way to the left.  Now your photo should look black and white.  If it doesn't, click and drag the layer that you just created to the top of the layer palette.

4. Hold down the shift key and click on the hue/saturation layer.  Continue holding shift and click on the top photo layer in the layer palette.  Now both of those layers should be highlighted blue.  Right click on either one of them and choose "merge layers".

5.   Now its time to add the color back in.  Select the eraser tool from your toolbar and choose a brush tip.  I like to turn the flow down to about 60% so that the color doesn't come back at its full intensity, but that is something you can experiment to see what you like.

6.  Begin erasing the black and white layer so that the color layer below shows through.  Make the brush tip bigger or smaller depending on the size of the area you are erasing.   Sometimes its helpful to zoom in really close (200% or more) so that you can make sure your edges are are clean.   If you make a mistake, simply undo the last action and try again.

7. I think that's it.  Remember to save as needed.

Let me know if anything is unclear and I'll try to straighten things out.