If you get weak water flow when you turn on the faucet, don't assume your water pressure has suddenly gone bad. You could simply have a filter screen, or aerator, that's clogged. Remove the aerator as shown in the photo, rinse it out and reinstall it. If it's corroded or worn, take it to a home center and pick up a new one. Most stores have a slick gauge you can screw your old aerator onto to determine which replacement to buy. If you can't find a replacement for your aerator, soak the parts in vinegar overnight, scrub them with an old toothbrush and reinsert into the faucet (make sure to reassemble the parts in the same order you removed them).
Weak water flow? Check for a clogged aerator first.