Species identification and related phytosociological characterisation is generally done by trained botanists and ecologists. However, amateurs can also record common species with the help of simple identification keys relating morphological attributes to the species type. Some easy guidelines for tree identification are available by Woodland Trust here.
Computer based software and mobiles apps have also been developed to aid species identification. For example, Tree ID app developed by the Woodland Trust helps to identify native and common nan-native tree species in the UK by following few interactive steps.
List and comparison of some other mobile based apps can be found here.