Use *like* in that 'similar to/ such as/ ' sense when nothing else needs to be stated in order to be completed and unambiguous.  

*he used to have a car **like** mine  
they were **like** brothers  
she looked nothing **like** Audrey Hepburn  
why are you talking about me **like** that?     
the cautionary vision of works **like** Animal Farm and 1984*  

Both your presumed to-avoid examples are grammatical.  
>Flying a plane is **like** driving a car but it's a bit more complicated. (similar to)
You can multiply a number by two to have an even number, **like** 3*2=6. (the same way as, for example)  

However, *like* is a poor choice in the first case because it is unclear here as to 'in what way/ in what respect(s)'; it even sounds like you contradict yourself later.  
>Flying a plane is <strike>like</strike> **similar to** driving a car but it's a bit more complicated. ('similar to' cautions that it is 'like but not the same').  

In the second case, the intention is to present a use-case/ example (3*2=6) to illustrate the process just stated (*multiply a number by two to have an even number*).

>You can multiply a number by two to have an even number, <strike>like</strike> **for example,** 3*2=6.  

Though *[like][1]* can function as more than one POS, has many uses and is probably the easiest to read and understand, it can easily make a statement ambiguous. Avoid it for that reason, in favor of a more precise word that makes the statement clear.


  [1]: http://www.oxforddictionaries.com/definition/english/like