As has already been mentioned, one of the best things you can do whilst honning your observation skills is to
slow down.
It gives you the time to take things in (on both a conscious & subconscious level). We have 5 senses for a good reason, if necessary use them all
Still hunting is a very good example of the benefits of this technique.
A still hunter will move
very slowly through the bush, taking the time to see, not just look, at what is within sight before moving on. The still hunter will also be acutely aware of wind direction, available cover, types of plants, animal spore, dry leaves on the ground, sun position etc, etc, etc).
If you are looking for a trainning technique to start the process, try cataloging everything within a small area (types of plants, location of the sun at that time, wind direction, lay of the land, cloud type and movement).
Given enough practice, this will become something you do without thinking about it.
Since IMO, bushcraft is about making use of the resources around you, observation skills are a vital part of Bushcraft because you become increasingly become aware of
all the available resources.
Hope this helps.
Kind regards
Mick