Reddit mentions of Rite in the Rain Weatherproof Hard Cover Notebook, 4 3/4" x 7 1/2", Yellow Cover, Journal Pattern (No. 390)

Field Collecting 101: The difference between a scientist and any old asshole who just pulls a plant out of the ground is data. You need to preserve as much information as you possibly can about the plant.

First, start a collection book. I like the Rite-In-The-Rain 390 (NOT the 390F). This is where you will store all the information about your collections.

Assign each individual collection a unique personal identification number. Start at number 1 and go up. Most people do something like [First Initial][Last Initial][Collection Number] - JD001 or whatever. The numbering system is your own for life and never resets when you change institutions. Each number should refer to one species collected from one location on a given day. Different species? Different number. Different location? Different number. Different day? Different number.

Write a site description for each location where you collect. This can be for one collection or for multiple collections from the same site. The site description should include:

which collections the description is relevant for
date
elevation
gps location
directions to site
associated species
list of collectors
description of the topography.

Then for each collection at the site i record:

collection number
presumed family
number of replicates
field identification (as close as i can get)
determination with date of det (usually done at a later time in office)
description (write down the characteristics of the plant that can be lost in the preservation - lifeform, maximum size, color, smell, taste, etc)

I generally collect 2-4 replicates of each species. In selecting specimens, try to find plants that have as much information as possible - perfect is when you have a full sized plant with flowers, fruits and roots fit on a single page. But that isn't always possible. Some plants are too big. Some plants don't flower and fruit at the same time.

A made up example for a full site description with a single collection could look like this:

Site Description for JD537, 17 June 2005.
Elev: 1987m W 114º14’31.9” N 37º22’47.0”
Directions: ~450m by air north of Quaking Aspen Spring. Clover Mountains. Lincoln County, Nevada. United States of America.
Ass.Spp.: Quercus gambelii, Pinus monophylla, Juniperus osteosperma, Artemesia tridentata, Gayophytum ramosissimum, Collinsia parviflora, Crepis occidentalis, Lotus plebeius, and Polygonum douglasii.
Coll: J. Doe with J. Schmoe and J. Blow
Topo: Flat ridge top. Rocky volcanic substrate.

JD537, Liliaceae, (3)
ID: Calochortus bruneaunis
Det: Calochortus bruneaunis Nels. & Macbr., 14 Nov 2005
Desc: Perennial herb from bulb to 45cm. Corolla yellow to white. Nectaries purple. Calyx green to purple.

Now that you have all that metadata written down, you can press the specimen. I use a different piece of newspaper for each replicate and write on the spine of each page: Collection Number, Field ID, Date, Replicate Number. For the previous example, the first replicate would be "JD537, CALBRU, 17 Jun 2005, 1 of 3"

Fill that press up! Stick it in the dryer til the plants are nice and crispy. Determine everything. Type up your labels. Mail replicates to various herbaria for mounting.