Self-censoring a First Draft

I offer two rules for this:
1. DON'T DO IT
2. DO IT
in that order.
First, as a beginning writer, an inexperienced writer at any age, it is essential that you not edit yourself as your write. Put it all down. Leave nothing out. The reason is simple: You are in the zone and don't want to miss out on anything, don't want to be limited. You will have plenty of time to revise, edit, censor later. Do not deviate from this.

Well, don't deviate until you have reached a more accomplished stage in your writing. At some point you may know and understand your own voice, may have worked in it enough so that you know what you are doing as you do it. At this point you may have read and learned enough about poetry so that you know what to cull on the fly. This is a much more efficient way to write than to write down all the claptrap you once needed to include and excise later when you could better make decisions. If you are not comfortable doing this, don't risk it. For my money you can't really get away with it during your first ten or so years of hard writing work. When you reach that point, don't bother any longer.