I save only the trim which is really covered in trichs. I even trim the tips off of what I'm saving. The less "green matter" that you are using the better.
I dry mine for about 24 hours, then bag them up and put them in the freezer.
I know subcools name is dirt in the section of RIU, but he has a really good sticky on bubble hash making. Short concise videos, which are easy to follow along to.
I have stepped my hash game up by water curing my lowers and trim. You can remove a lot of chlorophyll, salts, and other undesirable stuff from the material that you don't want in your hash by doing this first. I soak everything in a 5 gallon bucket for about 4-5 days, changing the water every 24 hrs. You will be amazed at all of the shit that will leach out of the buds/trim each time you change the water. The more stuff you can purge from the material prior to making the bubble hash, the more pure your end product will be.