All of these settings are available in the Window > Preferences dialog of Aptana Studio.
Unix Line Endings
To set UNIX line endings choose, go to the General > Workspace preferences. Choose "New text file line delimiter", "Other" and select "Unix" in the drop down.
Spaces, Not Tabs
To use spaces instead of tabs, go to General > Editors > Text Editors and check the "Insert spaces for tabs". Additionally, you might need to select "Use spaces" under the General tab of Aptana > Editors.
Character Encodings
Our files should all be encoded as UTF-8. To set the file encoding, go to Aptana > Editors > HTML and edit the default HTML template to look like this:
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
Other Settings You Might Want to Consider
If you prefer to limit your lines to 80 characters, you can add a print margin indicator to remind you when to wrap manually. Go to General > Editors > Text Editors and check the "Show print margin" and set the "Print margin column" to 80.