Remove the Aerator Before You Turn on the Water
Messing around with plumbing often dislodges minerals or other debris that has built up inside the pipes and valves. To prevent that stuff from clogging the aerator in your new faucet, remove the aerator before turning the water back on. The aerator is the device on the end of your faucet that has a screen or perforated plastic covering the end. Most aerators simply unscrew counterclockwise. Some new faucets include a special tool for removing the aerator.
If you're installing a pullout faucet, the aerator can be tricky to remove. If this is the case, simply unscrew the entire spray head from the supply tube and point the tube into the sink while you turn on the water. Let the water run a few seconds. Then replace the aerator or spray head. If your faucet ever starts to run slowly, remove the aerator and clean it. This will usually fix the problem.