User IDs: Can be found by mentioning the user then adding a \ such as \@YAGPDB.xyz#8760 . Alternatively if you have developer mode on, you can right click and select Copy ID. How to enable developer mode in Discord.
Channel IDs: Can be found by mentioning the channel then adding a \ such as \#announcements. Alternatively if you have developer mode on, you can right click on the channel and select Copy ID.
Role IDs: Use the listrolescommand.
If it is a custom emote, adding a \ in front of the emote such as \:yag: will display the name along with the ID such as <:yag:277569741932068864>. On an Android device remove backslash and enclose :yag: inside back-ticks `:yag:`.
If it is an animated emote, do the same steps as a normal emote. If you do not have Discord Nitro, you can have a friend or a bot use the emote and right click on the emote to open its link. The ID will be a part of the URL.
If it is a default emote, look up the Unicode for the emote on Google. Note that some of the more customized default emotes such as some of the family emotes will not work in any of the YAGPDB commands.