I have pretty much no hot water pressure in my spare bathroom shower. The shower hasn't been used for a while, and I am wandering if there is anyway something plugged up over time. If so how do you get it unplugged. My shower is just one individual nob. I have a lot of pressure at the sink and toilet in the same bathroom so I am thinking it is something in the wall. What is the best thing to do in this situation? Thanks in advance.

If all other hot water faucets are fine then I'd suspect you shower mixer is plugged up. Shut off your main and open the mixer, usually a screw in the knob or under a log cap. Under the knob you will see either a large hex ring or several screws, remove and pull the stem. You may have a valve stem or even a cartridge but most can be cleared of debris with a tooth pick and some blowing. Clean the shower head screen too. This would also be a good time to flush your hot water tank. Leave the main on for this but close off the fuel. Open the drain at the bottom of the tank and allow it to drain via a hose.