Step 1: shower rather than filling a hot bath. If you happen to shower in a bathtub, leave the plug in next time and compare the final water level to how deep it is when you run a bath. For most people showers use 1/4 to 1/2 the water of baths.
Step 2: shower less often. Your hair adjusts its oil production to your washing frequency, a fact you can easily confirm in a week's experiment. Every other day should be fine unless you are a manual labourer or construction worker. You might benefit from wearing deodorant on non-shower days. Showering every other day will cut your water use in half. If you're convinced you reek, a quick wipe with a warm facecloth for the parts of you that you believe are the problem will use almost no water, and it's ok that your elbows are going unrinsed for a day.
Step 3: turn the shower off while you do anything that takes time (shaving, applying hair conditioner, etc) in the shower. This has the smallest impact but could cut water use in half depending on the things you do in the shower. Also consider doing less in the shower: do you need to soap and then rinse every square inch of skin from head to toe? How did your elbows or the tops of your feet get so filthy they need soap? Surely they get clean enough just with the water running over them?
Step 4: cut your hair super short (but don't shave your head) so you don't need to do so much to it in the shower. Grow a beard so you don't need water to shave your face. Stop shaving or removing any body hair. Most people would reject these choices because they affect life outside the shower too.
Step 5: wash your hair in the sink (using about 2L of water) every other day, and clean yourself with a washcloth and warm water at the same time. Takes a little longer but could get water use down dramatically. Think of showers and baths as recreational activities rather than for cleaning yourself, and "spend" water when you want that experience. Probably what I would choose before Step 4.
Step 6: install some sort of greywater system so the water you shower and wash with is used for another purpose before you dispose of it. Ironically the more you concentrate the soap (and possibly dirt) in a smaller and smaller amount of water the less desirable your greywater is. But look into it anyway.