All forms of the verb "to be" can act as linking verbs, as are verbs that acknowledge a "sense" (proves that the subject exists). They serve primarily to "link" one subject to another. For example, "Mark was a sailor." This clearly identifies who and what Mark is, not what actions he performs.
The most common linking verbs are: am, appear, are, be, been, become, being, is, feel, look, remain, seem, smell, taste, was and were.
When it comes to simple recognition of the basic linking verbs (the various forms of "to be"), a common tool is often by utilizing a melody. The "ABC" song is a simple and effective way to help remember the verbs. Just about any simple tune will work, as long as the linking verbs that you want to remember are being used. Unfortunately, this will not teach you how to use the verbs, but simply teach what the common ones are.
Similarly, mnemonic devices can be used as well, but these can be difficult since most of the words begin with consonants.
Use the verbs in a sentence and having a student identify the verb type, subject, and complement in the sentence. As the student sees the verb in action, he will see how it is used.
Another possibility is writing the verb on one side and the types of verbs it can act as on the other side. This will help the student understand that many verbs can function as more than one type of verb.
Perhaps the most effective way to remember the linking verbs is to simply write sentences that utilize them. Remember that the subject and the complement must be equal; for example: James is a baseball player. The verb "is" links what James' occupation is. Simply put, James = player.
Since the "sense" verbs can sometimes be used as action verbs, it is important to use variety in the sentence structure. Basic structure memorization will aid in the recognition of how the verbs can be used.