While still in the field it is important to note what part of the intertidal zone you took the algae sample from (i.e. tidal height) and what substrate or other algae it was growing on. It is also important to note what the sample looks like before it is dried. What color is it? What does it feel like? Is it hard, soft, smooth, rough, squishy, silky or velvety? Is it elastic or stiff? Note whether the specimen is radially symmetrical (i.e. does it have similar parts regularly arranged around a central axis?) or growing flat on one plane? Use a hand lens to see finer details and write those down too.
In the field, remove the algae specimen from the substrate along with its holdfast. Wrap the specimens in newspaper and take them home with you. When you return home, immediately wash the specimens in a bowl of water. Label herbarium paper with a pencil indicating when and where you found the specimen. Allow the algae to fan out in the bowl of water and slip the herbarium paper into the water under the specimen, carefully raising the paper such that the algae adheres to the paper in its natural form. The specimens must be pressed and dried as soon as possible to prevent mold from growing. Layer the algae on the herbarium paper with layers of newspaper and cardboard to allow air to flow and facilitate drying. You will have to change the newspaper sheets and cardboard if they become too damp.