Titles are notoriously difficult but luckily they can be approached from so many different directions. You can go for a thematic title or a very descriptive one. Names of characters or even places can work wonders as a title. Both short or long title can work well in the right situation. The Lord of the Rings and The Hound of the Baskervilles are both excellent titles and are quite long, so in my opinion there really isn't any need to completely steer clear of long names. Sometimes giving plenty of information in the title is a good thing and helps grab people's attention. Think of Teenage Mutant Ninja Turtles, for example.
I think the key thing to avoid are titles that can easily be confused with a popular title. Unless, it's a parody or on purpose. The title doesn't have to be the most original one in the world but being recognizable is important. Another thing about recognizability is that the title needs to be easily remembered. A foreign title or an unusual word may sound good in theory but people may forget it quite soon.
In the end what matters the most is that you feel confident and comfortable with the title you've chosen. It can sometimes take a long time to come up with something that works (and isn't taken yet) but it's worth the struggle.