Learning how to light things can be fun and challenging both at the same time. However, it allows you the opportunity to try different things and work on some creative problem solving. I spent some time recently playing with a few different lighting setups at home and decided to put my guitars in front of the lens. There are a few challenges to deal with right off the bat such as their shape, and that fact they're shiny (i.e., they reflect light) so placement of your lights can be tricky. By making small adjustments you can find something that works.
My electric is a white Ibanez S540, which I wanted to place on a black background to put the focus on the guitar itself. I had some trouble with how I was going to do this because guitars don't sit very flat. I wanted to avoid using a guitar stand as I didn't want to do a lot of post work in Photoshop; I wanted to keep it simple in Lightroom. I decided to leave it in the case since it has a nice plush black interior, which would be easy to darken with a little bump of the Blacks slider in Lightroom. It was on the floor so I was hanging over it shooting down. I went for the Joe McNally approach on this and used all of the lights I had, which was really only 3 SB900s. One just above, one on the left and the third I placed by the headstock and skimmed it across to get some glint off of the strings. Post was all done in Lightroom.
For my acoustic I decided that leaving it on the stand was going to be easier so I placed it in front of a black background. I used a tight crop in camera to focus on the shape. This composition also allowed me to avoid having to remove bits of the stand in Photoshop as they were completely out of frame. I went minimal for this and used only one SB900 through a 24" Lastolite Ezbox on camera left. Post started in Lightroom then tripped over to Photoshop for some cleanup work, then back to light room for some finishing.
The amplifier was a similar set up to the acoustic. Placed it on a black backdrop with one SB900 through the same 24" Lasotilite Ezbox overhead on the left positioned almost like a shower head. My goal was to only light a portion of it and try and let the light fall off towards the bottom right. Post was all done in Lightroom.