Aliases in Ubuntu

[zongo saiba]

Hi, 

Two questions about creating aliases in Ubuntu
1) is it best practice to create an alias in ~/.bashrc or is it
preferable to create the alias in ".bash_aliases" ? If so, how do you
create an alias in ".bash_aliases" ? I can vim into ~/.bashrc but can't
seem to be able to vim into ~/.bash_aliases. I can cd into that
directory but it is empty since I have created my aliases into ~/.basrc.
2) Is it best to use single or double quote when creating aliases. 
ex: would alias dirA="echo Working directory is $PWD" be similar to
alias dirB='echo Working directory is $PWD'

Kind Regards, 

zongo