Here's a sample of a great nature journal entry (excluding the reflection):

Name: Chuck Brown

Date: September 12, 2002

Time of Day: (use nature and not a watch to indicate this) 

Mid-morning -the sun is only about half-way up in the sky

Location/Habitat:  The fields behind LHS and around the pond

Weather: Warm and sunny - warm enough  for a swim.

Focus Point: Find one "being" such as a plant, bird or  tree. Focus in and then sketch. Details in your sketch and written description of the "being" should indicate: color, size, texture, specific location and diversity (common or uncommon).

 Color: This leaf had several different shades of green with the veins and edges of the leaf being a different shade of green from the main body of the leaf.

Size:  About the size of the palm of my hand.

Texture: Smooth on the top, jagged on the edges and ribbed on the underside.

Specific Location: This leaf was on the end of a low hanging branch  of a  tree near the pond. 

Diversity: There are thousands of leaves like this one on this tree and many trees just like it nearby.