Best suggestion I can make is study and look up a lot of mythology, folklore, and general culture around the world during the times of antiquity and other old eras. It's a near endless well of inspiration for naming conventions that can also serve a dual role in potentially highlighting or providing context for a character's personality or traits in reference to the origin of their name. This is something that the creators of the Fire Emblem videogame franchise have done for years when it came to naming their characters for example.
Couple of things I can advice: - avoid too obvious parallels with real-life languages - calling a magical bear an Ursaror or something else taken directly from Latin like this is hammy and cheesy and stretches the suspension of disbelief to stupid levels. - common name for stuff doesn't have to be some sort of mumbled tongue twister - say, you have a flightless bird that kills prey by slamming it with its massive beak. You don't have to call it Ubrogorish, or some other cheesy crap like this. A common peasant would likely call this a hammerbeak, macebeak, maybe a flailhead and this is the type of name that would realistically stick. Sure, you can have names coming from various languages of the setting, but consider more pragmatic, common approach. - as for cities - consider the language of a culture and remember that many names of the cities come from some trait of the region, city itself or nearby famous event. Avoid too anglicised names, unless you go for something heavily based on English style, or unless you are 'translating' all the location names - and if you do, keep it consistent. Say, if you give your readers the names that sound remarkably English, like, I don't know, Twin Rivers, Leafshade, Oakspring etc. for human and elven villages, despite elves having vastly different language... and when you reach the... orc names for example and you roll out with some tongue twisters - you break the consistency here. It is an easy mistake to make, so avoid it. - avoid overly complex names for your characters, especially the main ones, unless you go for a joke with a lengthy naming conventions. Also avoid the names that are overly... obvious. Naming a villain a DARK LORD BAEL'KHERRIM is epitome of cheese - unless you go for some parody.
- get a word related to the thing that will be named, translate it to random languages until it sounds good, then change it a bit - watch some movies, read some books/comics or search for inspiration in music - stare at it until you randomly get a name for it