If you're lucky enough to have a "guest bathroom", one that isn't used by the family and one where you can always keep clean hand towels hanging for the guests, good for you. For most of us however, we have one or two bathrooms, and they both get a lot of use from the family members on a daily basis. Let's see how you can organize your bathroom so that it's guest ready too.
The one thing that most of us have too much of is lots of bottles of "stuff" sitting around the sink and countertop. Go through these and discard what you don't use on a daily basis, and what only has a drip left in it. Go buy two decorative baskets and have a "his" and "hers". One for his stuff, and one for her stuff. You could keep your toothpaste, hairspray, brush and comb, moisturizer, etc., in a basket that can be simply picked up and moved when guests come, and then put back when you're ready to use them again.
If you like to have magazines in the bathroom don't let them just pile up in a corner next to the toilet, get a nice magazine rack for them.
Next take a look at the inside of the shower. How moldy is that curtain? They cost around $4.00 - buy a new one. Look at the bottles in the shower, they tend to get left in the shower even when they're almost empty. Throw them out and try to streamline the number of bottles in the shower. If you don't have built in shelves around your shower get an organizer that hangs over your showerhead, or one on an extension pole you can put in the corner of the shower.
A cheap way to make your bathroom like new is with accessories. Buy a nice shower curtain with a matching rug. You can also get matching towels. If you have limited towel space you can buy a towel rack that hangs on the wall, they come in many different designs. With a nice wall towel rack you can make a display of beautifully colored towels - which you can also use too! Purchase a set of matching bathroom accessories, soap dish, toothbrush holder, cup, liquid soap dispenser.