If you are looking to hone your bird identification skills this article offers some great resources. A great article to start with is this Building Skills: The 4 Keys to Bird Identification from the Cornell Lab of Ornithology. This article gives you four observations to key into when watching birds, to help you narrow down your suspects and lead you to the identification. Often when birding you are not always lucky enough to spot the bird you are trying to identify and can only hear them. To hone your observations through bird song identification this article Bird ID Skills: How to Learn Bird Songs and Calls is a great place to start that process. As time goes on in your birding career you will find there are a few birds that you often mix up this Commonly Confused Birds article is a great resource to clear up some of those tricky birds. Lastly, as you go from backyard birds (or sometimes even in your backyard) you will want to hone certain groups of birds such as warblers or waterfowl. A great group to get started with deep identification are raptors here are some tips for identifying raptors.
Happy Birding!