If you already have a family tree program like 'Family Tree Maker' or 'Reuniion' I would use whatever their 'Export' feature defaults to. I have FTM and use it's GEDCOM 5.5 for export. It seems to work fine.
If you want a free version of family tree software to enter data and then produce a GEDCOM file this site looks at several: http://www.techsupportalert.com/best-fr ... ftware.htm
'Legacy' is the top of the list and I know several of our members like it.
Hope that helps. Ed McGuire