The first thing I do with my field guide is put my name and address in it so if I leave it behind, some kind soul will know where to mail it to.
Then I start to look at the photos and eventually read the introduction and other helpful information. Although I will admit it may take me a long time to get around to reading that helpful information and I am always shocked at how helpful it really is and wonder why I had never read it before.
Two years ago I went on a spider field trip and took the recommended Golden Guide Spider book along. It is a small book and really doesn’t have much room to write marginal notes so I tipped in 4 blank pages. Take a blank piece of paper, fold it in half and then trim it down slightly smaller than your guide. Next tape the folded edge into your book. Tape on both sides of the new pages to secure it in place. Vola! 4 more blank pages for notes.