I have hosted 2 ARK servers in my time, 1 on Abberation & now 1 on Ragarnok. About 2 years or so overall.
I wouldn't say there is a good way to get players to join, i've found being patient & putting a GOOD server name is KEY. After all this is the main thing players will look at & judge by. Maybe even skip the "Boosted" stats & keep it 2x rates for longer game progression.
People will Always come and go. But as a admin keep the server at it's best by cleaning unused/decaying bases & dinos. Run small little events to keep people entertained. Be active (Not always) in the chat.
Also, a good way to get people to join your server fast on Xbox is creating a group on ARK Survial in the 'Create a group' tab when clicking on the game. Although found people tend to leave quickly by doing this. But you can get over 10 people join at a time.