The key is to avoid looking like you have money/are an "outsider" as much as possible. That said, it's not like you walk around with a sign on you saying that you're staying at the Copacabana Palace so this shouldn't be an issue (maybe on a rainy day I would skip any hotel branded umbrellas, if they even exist).

Generally speaking, if you avoid walking "aimlessly" on the streets and just take cabs to anywhere you go you should generally be okay. The main tourist attractions (corcovado, sugar loaf etc.) are safe. One thing to note is that smartphones, (and iPhones specifically) are extremely expensive in Brazil, think $1000+, so they are common targets. Avoid showing/using it in public unless necessary.

I've said this many times but if you're looking to go to the beach, Rio is not the place to be. The beach there is average at best, which combined with the safety issues makes it a no go in my view. It's still in my (totally biased) opinion one of the most beautiful cities in the world, so you should definitely still go for the landscape/views.

Also, with all that said, I think that the outsiders view on Rio is generally much worse than the reality. Many on this forum have traveled to countries that are probably much more dangerous (like almost anywhere in Africa) and yet don't have the same "reputation". Be "smart" and you should have a great time.