First off, if you work where infectious diseases are prominent, have serious chemical sensitivity or mold issues, you probably need to purchase a respirator with a small micron opening such as the nanomasks that have shaped silicon holders. That said, most of us benefit from the reduction of incoming germs, without total protection, relying upon our immune systems to do the rest of the work.
The easiest thing to do for everyday exposures is to put a double or triple layered scarf over your nose and mouth and breathe through it while you are out in public places, or riding trains Cover the eyes with glasses or dark glasses and wear a pair of gloves, and you are good to go. In the summer just use a cotton scarf and sunglasses, and use your waterless hand cleaner after touching doornobs, bannisters and the like in public places. Make sure you wash well between uses.
If you want a bare-bones type of surgical mask and you can’t find then at your local pharmacy or Home Depot, you can cut a piece of old T-shirt that measures 8″x12″ . Fold it into thirds and insert shoelaces that will tie around your head. Usually 24″ -26″ will fit, but do test them out before going to the work of making the mask. You can also use a strong ribbon or cord. Put one shoelace along each long side, with the folded mask in the middle of the shoelace. What you should have will look like a sideways H with the mask part as the crossbar and the ties as the long sides. Stitch up the four sides, sewing into the ties and you are ready to secure them. Make several so you will remember to wash them between uses. You can also pull the cloth before sewing so you have more cloth around the nose, in the upper center. Here is an illustration of cotton masks, including one that uses elastic around the ears instead of head ties:
The New York Times has an amusing look at designer face covers of the low-density type:
If you are in a serious pandemic where you need to protect yourself, are volunteering to deal with the sick and can not get a respirator, you may need a heavy duty face mask. You can make one of these out of an old T-shirt too. You may want to bleach, wash and dry the T-shirt if it may have been exposed. Cut it into about nine pieces. The first piece should be wide enough to cover your nose and mouth comfortably, as shown above. The other eight squares should fit inside the part that goes over your face. You should alternate the way you place the grain of the squares. The mask should be tied tightly about the mouth and nose to be most effective. After using it, bleach and wash the mask.
No mask will help if you do not wear it. If you feel self conscious, you may want to decorate the mask with markers, preferably in a way that helps relieve tension since people will be feeling stressed out. This works best on paper masks, but can be done with the cotton masks as well. Just let the fumes dissipate before you wear the mask. Here is a picture from the Mirror showing one example:
New York Times: http://tinyurl.com/d6n2a9