Fungus (Deadaleopsis confragosa)
It is a good idea to try and decide what sort of wood they are growing on (brackets all grow on wood) as that will give you a further guide. Time of year is not such a good indicator as they can occur all year round but the rule of commonality will certainly apply - unless you are really lucky it will be the most common fungi you find.
The other vital piece of information you will require is whether the fungus you have found has gills on the underside or pores. Finally, and quite often key in any form of identification, not just fungi, is whether there is any particular feature that strikes you; on this fungi I was struck by the dark patches that look like bruises.
Armed with all this information it is then off to the field guide or reference book where all this information will be needed. In my guide, the pictures show that this could be one of several possibilities but the fact it has gills eliminated a group called the polypores. This one was in a rather damp woodland so I was pretty sure it was growing on a willow, there were no leaves on the tree at the time but it looked like Sallow to me. That brings down the choice again.
But the decider for me were these 'bruises'. They are a primary feature of Deadaleopsis connfragosa and that is how it gets its common name, the Blushing Bracket.