I originally thought I was supposed to create a groove, use an overstitch wheel, then use an awl to punch holes. When I went to my local Tandy store the sales person recommended a diamond CHISEL (I also thought chisels were for wood). They punch all the way through the leather, supposedly making the overstitch wheel and awl unnessesary. So, my question was asked to get the opinions of others on what they use. I have not purchased a single leather tool yet, I don't have the budget to buy unnecessary tools. I want to make the right purchase the first time I have included links to various chisels
http://www.csosborne.com/chisels_1.htm
http://www.tandyleatherfactory.com/en-usd/search/site-search-results.aspx?sectionpath=3&processor=content&p_keyword=Diamond+chisel