How can I boost the water pressure in my shower?
You should check to see what the water pressure is coming from the water main. A screw-on water pressure gauge can be connected to your garden hose connection to find out what it is. Ideally you would want to see a water pressure between 60 and 80 psi.

If your pressure is significantly lower than 50 psi from the main, then you will have issues with having enough pressure for most shower heads. If you have city water, you may have a water pressure reducing valve. These are typically installed near the water meter. If your house is equipped with one, take a measurement of the water pressure, and then incrementally tighten the screw and take measurements. If the pressure is too high, you can loosen the screw. You want to avoid water pressure over 100 psi. When the pressure is too high, it can cause damage to your plumbing system.

If you have a pressure issue at the main, this may fix your shower issues. If the main is not the problem, or you find the pressure is still too low, then the problem is somewhere in your plumbing system. If the pressure is good in the tub and sink in your bathroom, then the shower head itself might be the culprit. Unscrew the shower head itself and see if the pressure is good coming out of the wall. If that is good, then the shower head is clogged up and should be cleaned out or replaced. Certain shower heads contain a water saving feature that basically causes less volume of water to come out. They work fine in areas that have excellent water pressure such as cities, but not so much when you are running off of a well. In some cases the water saver part is removable. If it can be removed, then this may also fix the problem. Shower heads are pretty easy to replace. There are ones on the market which are specifically designed for low water pressure. Using one of those may help the problem, but if the water pressure is terrible, you may need to have a plumber inspect your entire system to find out where the problem is.