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As lonehorseend said, it's important to make sure characters seem different - but adding the character's names is very important. Case in point - go read some of the I Am Number Four novels, parti...
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#3: Attribution notice added
Source: https://writers.stackexchange.com/a/8516 License name: CC BY-SA 3.0 License URL: https://creativecommons.org/licenses/by-sa/3.0/
#2: Initial revision
As lonehorseend said, it's important to make sure characters seem different - but adding the character's names is very important. Case in point - go read some of the _I Am Number Four_ novels, particular the second and third novels. They swap (in third person) to different characters, without even using asterisks as breaks. It's nearly impossible to determine which character is which, and it makes for a very confusing read. Even if you have to fall to traditional tropes, make your characters unique. Eg, have a 'bitter and moody' character, a 'mysterious past' character, a 'ditzy, but means-well' character etc. Overplay it a little bit, but the reader will clearly understand the differences between the POVs. To be honest, I would go with placing the character's name at the start of the chapter - if you even think for a moment that a reader might get confused, then don't be ambiguous about it, and put the name there. There's no harm in putting it in.