If you have Battle.net, Makemehost.com (AKA Mbot/MMH) and Entgaming.net websites allow people to host and find games on there across all battle.net servers. Bassically, games hosted from those services can be joined on from any server.
Otherwise I don't have any tips if you do not have battle.net.
EDIT: So basically makemehost, ent and a few others are partnered togethe. If you go on makemehost.com and click game and queue list you can click the all button and it will show all the games that are being user hosted at top, and auto hosted at the bottom. They only show lobbies.