How can I create floating objects in After Effects?
This is accomplished during shooting and is not an editorial effect. An set of DSLRs (digital still cameras) arranged in an arc are triggered to all take a shot at the same instant. The individual frames are strung into a sequence and treated as a motion clip. There are lots of examples of this on the web.

You can do similar things using CGI, but it's not a simple task and it isn't cheap.

Edit:

You asked for a tutorial but I don't know of any, so...

Here's a demonstration

Here's a cheaper alternative