How can I set defaults for the various attributes on issue entry?
Right now, that is what issue templates do. Click on the ‘Templates’ link in the left hand side navigation, create the template and it will then show up when you go to enter a new issue. You can create as many templates as you wish and just ‘apply’ them when you enter a new issue. A nice feature addition would be to have a setting on the template administration screen that denotes which one should be automatically applied.