Outlets should be installed with the ground on the bottom so the hot side (narrower opening) is on right.
Make sure the black wire goes on the hot side.

Home wiring circuits usually are 15 amp. Some places like bathrooms and kitchens which may require higher power consumption appliances, Microwaves, Hair Dryers, etc. may have 20 amp circuits, although most of even these high power appliances will work on 15 amp circuits.

15 amp circuits require 14 gage (AWG) wire
20 amp circuits require 12 gage wire 
 (Note size goes up as gage goes down)

Your circuit breaker should indicate the amperage.

A while back 20 amp outlets were changed 
so the neutral side was a T shape to accomodate plugs
 with the neutral terminal at right angle to the hot.

About the same time 20 amp outlets eliminated the push in wire connection.
You have to wrap the wire around the screws. A pain with 12 gage wire which is stiffer.
Most outlets are tamper-resistant now. This is a safety feature to prevent children from sticking something in the socket. There is a spring-loaded thermoplastic safety shutter inside which requires something in both terminals to allow a connection.
This makes them harder to insert plugs, but they will loosen up over time.

last updated 23 Apr 2017