An easy way? Not really! These verbs have different histories in English
usage, so they overlap in confusing ways for the learner. They combine
subtleties of meaning (vocabulary) as well as form (grammar), so the
teacher's job is to provide examples that clarify those subtleties.
Learners can benefit from seeing examples of these distinctions. However,
those examples will naturally introduce the confusion of grammatical
forms that accompany each verbdirect and indirect objects, infinitives
and that-clauses, etc.
Perhaps the best we teachers can do is (a) teach the basic structures
and (b) caution against the most common errors, such as
X They said me
X I told that I
Say, tell, speak, and talk have different
meanings, but far more important to learners are the different grammatical
patterns that each verb takes. The main difficulty for learners is 1)
whether a verb can take a direct object or indirect object or both;
and 2) if it does, what kinds of object constructions are possible.
There is no easy way to learn these distinctions, but teachers should
be aware of the grammatical properties of each verb. Click
here for a summary.