Where can I put local latex style files and packages?

Create a folder in your root directory called texmf. Then create the directories inside it: tex/latex. You can do it all with one command:

mkdir -p texmf/tex/latex.  

Inside the latex directory, you can put your files (.tex, .sty, etc.) or
local packages.  You can create separate directories to organize your
files as well.

If custom bibtex style files (extension .bst) have been provided, place
these into a similar tree of the form

| $HOME/texmf/bibtex/bst/ |

Inside the texmf/tex directory, you can create other folders for amstex,
tex, etc. so you can organize the different kinds of tex files you have.
You can look at the shared localtexmf directory for an example of how to
structure your files in /usr/ias/localtexmf or /usr/share/texmf

Afterwards, run texhash or mktexlsr so that the programs will know to
look in your local texmf directory for all your files. Texhash will create a database of files inside your texmf directory. The database file is called, appropriately enough, "ls-R", and is located in the top level texmf directory, i.e., the file is | $HOME/texmf/ls-R |. The |ls-R| file is an ordinary text file and can be inspected with an editor or a pager like |more| or |less|. If the texhash run was successful, this file should contain a listing of all files under your private texmf directory.

Another option is to use the environment variable called TEXINPUTS, but it's more error prone...if you do use TEXINPUTS, be sure to set an empty dir as part of your list, ie
export TEXINPUTS=::/path/to/mydir