read

A global .gitignore file can also be used by adding one to your global git config. For example, you might create the file ~/.gitignore_global and add some rules to it. To add this to your config, run git config –global core.excludesfile ~/.gitignore_global

Some good rules to add to this file:
<pre style="background-image: URL(http://2.bp.blogspot.com/_z5ltvMQPaa8/SjJXr_U2YBI/AAAAAAAAAAM/46OqEP32CJ8/s320/codebg.gif); background: #f0f0f0; border: 1px dashed #CCCCCC; color: black; font-family: arial; font-size: 12px; height: auto; line-height: 20px; overflow: auto; padding: 0px; text-align: left; width: 99%;"> # Compiled source #
###################
*.com
*.class
*.dll
*.exe
*.o
*.so
# Packages #
############
# it's better to unpack these files and commit the raw source
# git has its own built in compression methods
*.7z
*.dmg
*.gz
*.iso
*.jar
*.rar
*.tar
*.zip
# Logs and databases #
######################
*.log
*.sql
*.sqlite
# OS generated files #
######################
.DS_Store*
ehthumbs.db
Icon?
Thumbs.db </pre><div class="line" id="LC1" style="font-family: monospace; white-space: pre;"></div>
<div class="line" id="LC1" style="font-family: monospace; white-space: pre;"></div>

Create file “.gitignore” in the root folder of the project with the contents:

<div><pre style="background-image: URL(http://2.bp.blogspot.com/_z5ltvMQPaa8/SjJXr_U2YBI/AAAAAAAAAAM/46OqEP32CJ8/s320/codebg.gif); background: #f0f0f0; border: 1px dashed #CCCCCC; color: black; font-family: arial; font-size: 12px; height: auto; line-height: 20px; overflow: auto; padding: 0px; text-align: left; width: 99%;"> *.class
# Package Files #
*.jar
*.war
*.ear
</pre>

Some good ignore files for any kind of projects or languages will be found in:

Ignore files
Source 1
Source 2 </div>