There are some good neighborhoods in St. Louis and some not so good neighborhoods. Generally, a lot of the crime/murders take place in the North side. Although, you can fall victim to crime anywhere I'd generally advise you to live in these areas:
My top 5 Neighborhoods:
2.) St. Louis Hills
3.) Tower Grove East
4.) Shaw - This place is getting better year by year. A really nice neighborhood
5.) Central West End - Pricey but very nice and seems to be the most popular with people out of town
There are a ton of other good areas but I'd definitely recommend those for someone fresh in the city.
And here's a crime map Just so you can get a look at where the crimes are most frequent and what kind of crimes are committed. Lol, coming from a small town in Central Illinois you might be shocked at how much people talk about crime but if you avoid certain areas St. Louis is a pretty safe place. I just trust in God and carry on my business. If you have any other questions do let me know.