Hello, i have been making pixel art for a good few years. but i have also been using photoshop for a good deal longer and it has always been my greatest tool in creating pixel art. so i am going to show a technique i have been using with some of my latest pices that have gotten some notification.
*note some techniques i use can be found here as well
http://danfessler.com/blog/hd-index-painting-in-photoshopfirst i start with the base picture

then add filters to first restrict it to a color pallet and resize if needed. in photoshop this can be done with postorize and gradient map.

After this you want to add a ditter pattern and blend it with the picture. in photoshop you create a new layer put it to soft light / over lay and play around with the fill / Opacity

now you already have a pixel art looking picture. and this is what my first picture i made was no real edits just a little cleaning.
if you want to make this your own you will put the color restirction to 1 or 2 colors and work from that like so.

now you have a base to work on. and a good referral you can make something crazy like this.

remember to always have the original you worked on if you are showing it off and say that you used a color reduction technique.