Tips for playing own ceremony music

Have some one man the phone and speakers who is good at this.

Label all songs very clearly when they are supposed to be played e.g. bridesmaids, bride, recessionary etc. Print out an outline of the ceremony and a list of songs.
When you make your Playlist make sure to chose the right version of the song.
If you make your Playlist with spotify e.g. purchase the premium version for your wedding month so that you don't have any adds playing.
It's better if whoever plays DJ for you uses their own device because they know that better.
I would download all songs unto device in case the internet connection is bad.

Talk about if they should play the whole song or when to stop/fade out.

For our wedding we had live music for the ceremony but we used a phone and speakers for the reception (no dancing). I had made four playlists in spotify and my friend downloaded all of them onto her iPad before. They were labeled cocktail hour background, entrance (just one song), dinner music background, first dance (just one song). It worked great. She just had to press stop and play basically. Another friend made announcements throughout reception. I had given both written instructions a few days before which helped them to feel like they knew what they were doing.

Great advice above. We also used speakers and our phone for our ceremony music since we got married on the beach. We had it all ready and just had a friend use our phone to control it all. Good luck.